Agents and fellow-thespians (7)
I believe the answer is:
factors
'agents' is the definition.
(I've seen this before)
'fellow-thespians' is the wordplay.
'fellow' becomes 'f' (abbreviation - of a society etc.).
'thespians' becomes 'actors' ('actor' can be a synonym of 'thespian').
'f'+'actors'='FACTORS'
'and' acts as a link.
(Other definitions for factors that I've seen before include "Agents" , "Circumstances that contribute to a result" .)