Fine cast members and parts (7)
I believe the answer is:
factors
'parts' is the definition.
(I know this)
'fine cast members' is the wordplay.
'fine' becomes 'f' (abbreviation in pencil classifications).
'cast members' becomes 'actors' (I've seen this in another clue).
'f'+'actors'='FACTORS'
'and' is the link.
(Other definitions for factors that I've seen before include "Circumstances that contribute to a result" , "Agents" .)