Spin a Dark Web/Soho Incident (1956)

A Canadian living in London is trying to succeed as a prizefighter, without much luck. He meets the sister of a local mob leader, and she soon draws him into the gang's activities. After he finds himself being drawn into a murder plot, he finally realizes that his lover is only using him, and determines to escape the gang, but things don't turn out the way he planned.

IMDb: https://www.imdb.com/title/tt0049774