Ruth's bottom pinched by green parrot (4)
I believe the answer is:
echo
'parrot' is the definition.
(both can mean to imitate or copy)
'ruth's bottom pinched by green' is the wordplay.
'bottom' says to take the final letters.
'pinched by' indicates putting letters inside (inserted letters get pinched or taken).
'green' becomes 'eco' (abbreviation for ecological).
The final letter of 'ruth' is 'h'.
'h' going into 'eco' is 'ECHO'.
(Other definitions for echo that I've seen before include "Reflection of sound wave" , "Reflect in Czechoslovakia" , "Before foxtrot" , "Sound bouncing back" , "letter we hear" .)