Parrot screech, one's assumed (4)
I believe the answer is:
echo
'parrot' is the definition.
(both can mean to imitate or copy)
'screech one's assumed' is the wordplay.
'assumed' says the answer is hidden in the clue (the answer is held or assumed by the clue).
'ECHO' is hidden in the letters of 'screech ones'.
(Other definitions for echo that I've seen before include "Reverberate - nymph spurned by Narcissus" , "repercussion" , "Comms code word for E" , "letter we hear" , "Reflected sound" .)