One fan accepts penny contribution (5)
I believe the answer is:
input
'contribution' is the definition.
(I've seen this before)
'one fan accepts penny' is the wordplay.
'one' becomes 'I' (Roman numeral).
'fan' becomes 'nut' (both can mean an enthusiast).
'accepts' indicates putting letters inside.
'penny' becomes 'p' (short for pence).
'nut' placed around 'p' is 'nput'.
'i'+'nput'='INPUT'
(Other definitions for input that I've seen before include "Signal supplied to a device" , "Comment, contribution" , "Data entered to computer" , "Resource" , "contributed information" .)