Limit a testament that displays copies (8)
I believe the answer is:
imitates
'copies' is the definition.
(I know this)
'limit a testament that displays' is the wordplay.
'that displays' says the answer is hidden in the clue.
'IMITATES' can be found hidden inside 'limit a testament'.
(Other definitions for imitates that I've seen before include "Mimics or simulates" , "Copies, simulates" , "Copies, takes off" , "Apes" .)