Terrific, parrot having heart transplant? (3)
I believe the answer is:
ace
'terrific' is the definition.
(thesaurus)
'parrot having heart transplant?' is the wordplay.
'parrot' becomes 'ae' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'having' indicates putting letters inside.
'heart' says to take the centre.
'transplant?' becomes 'act' (transplant is a kind of act).
The middle of 'act' is 'c'.
'ae' going around 'c' is 'ACE'.
(Other definitions for ace that I've seen before include "Dab hand" , "In golf, a hole in one" , "star" , "Tennis winner" , "smashing" .)