Compassion, we hear, for male deer (4)
I believe the answer is:
hart
'male deer' is the definition.
(I've seen this before)
'compassion we hear' is the wordplay.
'compassion' becomes 'heart' (I've seen this in another clue).
'we hear' indicates a 'sounds like' (homophone) clue.
'heart' sounds like 'HART'.
'for' is the link.
(Other definitions for hart that I've seen before include "Deer; Lorenz --, lyricist" , "Male red-deer" , "Animal" , "Ruminative type" , "Mature male deer" .)