Compassion, reportedly, for deer (4)
I believe the answer is:
hart
'deer' is the definition.
(I've seen this before)
'compassion reportedly' is the wordplay.
'compassion' becomes 'heart' (I've seen this before).
'reportedly' indicates a 'sounds like' (homophone) clue.
'heart' is a homophone of 'HART'.
'for' acts as a link.
(Other definitions for hart that I've seen before include "Richard Rodgers and Lorenz . . . . were famous musical partnership" , "Songwriting partnership, Rodgers and --" , "Mature male deer" , "Ruminative type" , "Adult male red deer" .)