Expensive-sounding stag (4)
I believe the answer is:
deer
'stag' is the definition.
(I've seen this in another clue)
'expensive-sounding' is the wordplay.
'expensive' becomes 'dear' (similar in meaning).
'sounding' shows a homophone (sound like).
'dear' is a homophone of 'DEER'.
(Other definitions for deer that I've seen before include "Hoofed mammal" , "Antlered mammal" , "The - Hunter, 1978 film" , "The male has antlers" , "Wild animal" .)