Provide a conclusion that's painful! (5)
I believe the answer is:
endow
'provide' is the definition.
(I've seen this in another clue)
'a conclusion that's painful' is the wordplay.
'a conclusion' becomes 'end' (something's conclusion is its end).
'that's painful' becomes 'ow' (I've seen this in other clues).
'end'+'ow'='ENDOW'
(Other definitions for endow that I've seen before include "Provide funds" , "Bestow" , "Attribute abilities to" , "Give qualities or abilities to" , "Settle permanent income on" .)