Sentence:  But slowly they take over as Alain Delon ( Life , Sept. 15 ) , <WSD>playing</WSD> a sometimes appealing but always criminal boy , casually tells a rich and foot-loose American that he is going to murder him , then does it even while the American is trying to puzzle out how Delon expects to profit from the act . 
Meaning of the word marked with <WSD> tags:  play a role or part