Take-off always including elevated material (5)
I believe the answer is:
apery
'take-off' is the definition.
(both can mean an instance of mimicry)
'always including elevated material' is the wordplay.
'always' becomes 'ay'.
'including' indicates putting letters inside.
'elevated' is a reversal indicator.
'material' becomes 'rep' (rep is a kind of material**).
'rep' written backwards gives 'per'.
'ay' enclosing 'per' is 'APERY'.
(Other definitions for apery that I've seen before include "Take-off" , "Imitative behaviour - repay (anag)" , "Mimicry" , "imitation" .)