What about cold duck or parrot? (4)
I believe the answer is:
echo
'parrot?' is the definition.
(both can mean to imitate or copy)
'what about cold duck' is the wordplay.
'what' becomes 'eh' (sound used to ask 'what?' or 'pardon?').
'about' means one lot of letters goes inside another.
'cold' becomes 'C' (eg on taps).
'duck' becomes 'o' (resembles zero - 'duck' in cricket).
'eh' placed around 'c' is 'ech'.
'ech'+'o'='ECHO'
'or' acts as a link.
(Other definitions for echo that I've seen before include "Sound following" , "ring" , "Return of sound waves" , "Close imitation" , "Languishing nymph" .)