Pithy part for Peter Sellers (5)
I believe the answer is:
terse
'pithy' is the definition.
(I've seen this before)
'part for peter sellers' is the wordplay.
'part' indicates a hidden word.
'TERSE' is hidden within 'for peter sellers'.
(Other definitions for terse that I've seen before include "Pithy and concise" , "Brusque and curt" , "Briefly expressed" , "Short and sharp" , "Crisp and brief" .)