Expensive for an animal by the sound of it (4)
I believe the answer is:
dear
'expensive' is the definition.
(I've seen this before)
'an animal by the sound of it' is the wordplay.
'an animal' becomes 'deer' (I've seen this before).
'by the sound of it' shows a homophone (sound like).
'deer' sounds like 'DEAR'.
'for' is the link.
(Other definitions for dear that I've seen before include "Pricey" , "polite form of address" , "Needing plenty of bread" , "Honey - costly" , "Costly (but loved!)" .)