Agents get fine cast (7)
I believe the answer is:
factors
'agents' is the definition.
(I've seen this before)
'get fine cast' is the wordplay.
'get' means one lot of letters go next to another.
'fine' becomes 'f' (abbreviation).
'cast' becomes 'actors' (I've seen this before).
'f' next to 'actors' is 'FACTORS'.
(Other definitions for factors that I've seen before include "Circumstances that contribute to a result" , "Agents" .)