Influence of fine performer (6)
I believe the answer is:
factor
'influence' is the definition.
(I've seen this before)
'fine performer' is the wordplay.
'fine' becomes 'f' (abbreviation in pencil classifications).
'performer' becomes 'actor' (actor is a kind of performer).
'f'+'actor'='FACTOR'
'of' acts as a link.
(Other definitions for factor that I've seen before include "Mathematical quantity" , "Reason" , "Number by which another is exactly divisible" , "One circumstance that contributes to a result" , "Scottish estate manager" .)