Nails cut up (4)
I believe the answer is:
boom
'up' is the definition.
(thesaurus)
'nails cut' is the wordplay.
'nails' becomes 'booms' ('boom' can be a synonym of 'nail').
'cut' means to remove the last letter.
'booms' with its last letter taken off is 'BOOM'.
(Other definitions for boom that I've seen before include "Period of prosperity - explosive sound - sailing boat's spar" , "When business is great, opposite to bust" , "sound of artillery fire" , "become suddenly prosperous" , "Floating barrier" .)