Do office work for fifty pence piece! (4)
I believe the answer is:
type
'do office work' is the definition.
(I've seen this in another clue)
'for fifty pence piece' is the wordplay.
'piece' indicates a hidden word.
'TYPE' is hidden in the letters of 'for fifty pence'.
(Other definitions for type that I've seen before include "Kind, model" , "of a certain kind" , "key" , "Class or group of a particular class" , "Stamp" .)