Give conclusion: that hurts! (5)
I believe the answer is:
endow
'give' is the definition.
(I've seen this before)
'conclusion that hurts' is the wordplay.
'conclusion' becomes 'end' (end is a kind of conclusion).
'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" .)