Part of cylinder coming out of trap? (4)
I believe the answer is:
role
'part' is the definition.
(synonyms)
'cylinder coming out of trap?' is the wordplay.
'cylinder' becomes 'roll' (roll is a kind of cylinder).
'coming out of trap?' shows a homophone (sound like) (trap can informally mean one's mouth).
'roll' sounds like 'ROLE'.
'of' is the link.
(Other definitions for role that I've seen before include "Playing part" , "Duty" , "Part, portrayal" , "Acting part" , "Impersonation" .)