Unfinished clue ain't revised? That's crazy (7)
I believe the answer is:
lunatic
'crazy' is the definition.
(I've seen this before)
'unfinished clue ain't revised?' is the wordplay.
'unfinished' means to remove the last letter.
'revised?' indicates an anagram.
'clue' with its last letter taken off is 'clu'.
'clu'+'aint'='cluaint'
'cluaint' with letters rearranged gives 'LUNATIC'.
'that's' is the link.
(Other definitions for lunatic that I've seen before include "Deranged" , "nut" , "fruitcake" , "crazed?" , "Mad" .)