Handle the first expression of pain (5)
I believe the answer is:
touch
'handle' is the definition.
(touch can mean to feel or handle)
'the first expression of pain' is the wordplay.
'the first' becomes 't' (1st letter of 'the').
'expression of pain' becomes 'ouch' (I've seen this before).
't'+'ouch'='TOUCH'
(Other definitions for touch that I've seen before include "Side beyond playing area" , "Deal with" , "Make physical contact" , "Graze" , "Move" .)