Give conclusion: that hurts! (5)
I believe the answer is:
endow
'give' is the definition.
(endow can mean to give or bestow)
'conclusion that hurts' is the wordplay.
'conclusion' becomes 'end' (something's conclusion is its end).
'that hurts' becomes 'ow!'.
'end'+'ow'='ENDOW'
(Other definitions for endow that I've seen before include "Provide with a permanent income - perhaps a college" , "Present with a source of income" , "Woden (anag.)" , "Give qualities or abilities to" , "Settle permanent income on" .)