In 1980, Gilyard moved to Los Angeles to become an actor. He became the first black actor to undertake the role of the cheerleader in the play "Bleacher Bums" before he segued into television roles. As a character actor, Gilyard has made guest appearances on TV shows such as "Diff'rent Strokes," "The Facts of Life," "227," "Simon & Simon" and "Riptide." In 1982-1983, Gilyard was cast in the final season of the NBC TV series "CHiPs" as Officer Benjamin Webster. He co-starred with Jim Carrey in the 1984 NBC sitcom, "The Duck Factory."

Aside from acting, he appeared in at least one commercial for McDonald's in 1987, Gilyard's movie debut in 1986 was as Radar Intercept Officer (RIO) Sundown in "Top Gun." He was also a military man in the 1986 film "The Karate Kid, Part II." He appeared in the 1988 action film "Die Hard" as Theo, a computer expert and terrorist. He also appeared as Reverend Bruce Barnes in "Left Behind: The Movie" and its sequel, "Left Behind II: Tribulation Force."

By the end of the 1980s, after years as a struggling actor, he finally found the role that would make him famous as Andy Griffith's private investigator, Conrad McMasters, on "Matlock." He replaced Kene Holliday, who had a dependency on drugs and alcohol. Like his co-star, Nancy Stafford, who played Michelle Thomas in the series, Gilyard had been a fan of Griffith's since the 1960s.

He once said that when auditioning for "Conrad," he forgot the script and became Opie Taylor (played by Griffith's former co-star Ron Howard). On the show, Gilyard performed some of his own stunts and had a wonderful on- and off-screen chemistry with Griffith. Unlike many of his 'Matlock' co-stars, with the exception of Holliday and Daniel Roebuck (who replaced Gilyard in 1993), Gilyard appeared in almost every Matlock episode during his three seasons on the show. After the show moved from NBC to ABC for the series' seventh season, Gilyard departed to work on a pilot for another series at CBS.

In 1993, he began another longtime co-starring role opposite Chuck Norris on "Walker, Texas Ranger." Gilyard portrayed fellow Texas Ranger and best friend of Walker, James "Jimmy" Trivette. The show proved to be a big hit. Gilyard again enjoyed the chance to perform stunts. The chemistry between Norris & Gilyard made for memorable 1990s television and included Noble Willingham, who played C.D. Parker in the show's six seasons. All three actors were good friends on and off the set.

During a 2005 interview with A&E Biography, Gilyard said that Norris's Walker character was a cult-classic Western hero. Gilyard also recalled that when he and Norris were growing up, other Westerns they watched often had characters that served as surrogate father figures. He noted that he and Norris had served in the Air Force, albeit sixteen years apart.

Near the end of the Walker series, Norris's character married his longtime girlfriend, an assistant district attorney played by Sheree J. Wilson, while Gilyard's character was given a girlfriend. Gilyard remained in the Trivette role for the entire run of the series. In his television career, Clarence has been fortunate enough to co-star with two TV legends on two successful series over the course of 12 total seasons.

Gilyard appeared in the 2005 television movie, "Walker, Texas Ranger: Trial by Fire," but only had a cameo appearance because the filming schedule conflicted with a long-planned family vacation.