Compassion before defeat showing sign of life (9)
I believe the answer is:
heartbeat
'sign of life' is the definition.
'compassion before defeat' is the wordplay.
'compassion' becomes 'heart' (I've seen this before).
'before' says to put letters next to each other.
'defeat' becomes 'beat' (synonyms).
'heart'+'beat'='HEARTBEAT'
'showing' is the link.
(Other definitions for heartbeat that I've seen before include "Circulation noise" , "Animating force" , "Pulse of cardiac origin" , "Essential pulsation" .)