Copy restriction? Not at first (9)
I believe the answer is:
imitation
'copy' is the definition.
(I know that imitation is a type of copy)
'restriction? not at first' is the wordplay.
'restriction?' becomes 'limitation' ('limitation' can be a synonym of 'restriction').
'not at first' means to remove the first letter.
'limitation' with its first letter taken off is 'IMITATION'.
(Other definitions for imitation that I've seen before include "Simulated" , "take-off" , "it's not for real" , "It's said to be the sincerest form of flattery" , "created by the impressionist" .)