East Side Kids

In 1942, he was loaned to Monogram Pictures. Among his friends, he was known offscreen as "Stosh", so he adopted the nickname "Stash" in the ensemble-cast film series the East Side Kids. He appeared as an East Side Kid in Smart Alecks, 'Neath Brooklyn Bridge, and Ghosts on the Loose. He retained the character name of "Stash" in other films: Right to the Heart, Military Academy with That Tenth Avenue Gang, and Boots Malone.

Marriage

In August 1945, Clements married actress Gloria Grahame, who played Violet Bick in It's a Wonderful Life, and who later won a Best Supporting Actress Oscar for The Bad and The Beautiful. The marriage was a stormy one, with Grahame objecting to Clements's drinking and gambling, and Clements being jealous of her dalliances with other men, and it ended in 1948. He married Maria Walek in 1951. In 1964, they adopted her eight-year-old nephew, Sylvester, bringing him to the United States from Poland.

Other roles

After the East Side Kids, Clements then set out on his own again, this time landing roles in more prestigious pictures. He was featured in perhaps his best-known role as Tony Scaponi in the 1944 Bing Crosby film Going My Way, and scored a great success as a jockey in the 1945 Alan Ladd feature Salty O'Rourke.

Clements's acting career was interrupted by U.S. Army service as a private first class just after World War II. When he returned in 1947, he began appearing in more adult roles in lower-budgeted films, including Johnny Holiday (cast against type as a psychopath) and Destination Murder (as a hired killer). He starred in a series of action/detective pictures at the successor to Monogram Pictures, Allied Artists, for producer Ben Schwalb and director Edward Bernds.

The Bowery Boys

In 1945, after Leo Gorcey left the East Side Kids in a salary dispute with producer Sam Katzman, Gorcey's teammate Bobby Jordan arranged a meeting with his agent, Jan Grippo. Gorcey partnered with Grippo to produce a new "gang" series called The Bowery Boys, with Gorcey owning a 40% share in the franchise. Gorcey's real-life father Bernard Gorcey was added to the cast as Louie Dumbrowski, proprietor of Louie's Sweet Shop, the headquarters of The Bowery Boys. Younger brother David Gorcey, formerly one of the East Side Kids, returned to appear in the new series.

After Bernard Gorcey was killed in an auto accident in 1955, a grief-stricken Gorcey turned to alcohol for solace and became a disruptive presence in the studio during the filming of Crashing Las Vegas, trashing scenery and destroying props. In 1956, Gorcey demanded a larger share of ownership from Allied Artists, which was denied, and after a heated conversation, Gorcey stormed off the studio lot and quit the series.

When the series's then-producer Ben Schwalb needed a replacement for Gorcey, he asked Clements to step in as The Bowery Boys' new ringleader, Stanislaus "Duke" Coveleskie (although Huntz Hall received top billing). Clements comfortably settled into the role of Huntz Hall's sidekick, and co-starred in the final seven Bowery Boys comedies, beginning with Fighting Trouble.