Compassion improves each anguish (9)
I believe the answer is:
heartache
'anguish' is the definition.
(I've seen this before)
'compassion improves each' is the wordplay.
'compassion' becomes 'heart' (I've seen this in another clue).
'improves' indicates anagramming the letters (I've seen 'improved' mean this).
'each' is an anagram of 'ache'.
'heart'+'ache'='HEARTACHE'
(Other definitions for heartache that I've seen before include "Emotional distress" , "Great sadness" , "Agony of Love" , "Emotional anguish" , "Suffering" .)