Bother: our belt is ruined! (7)
I believe the answer is:
trouble
'bother' is the definition.
('trouble' can be a synonym of 'bother')
'our belt is ruined' is the wordplay.
'is ruined' indicates anagramming the letters.
'our'+'belt'='ourbelt'
'ourbelt' with letters rearranged gives 'TROUBLE'.
(Other definitions for trouble that I've seen before include "Dire straits" , "Discord" , "Difficulty; cause distress to" , "Effort - (cause of) worry" , "Difficulty, problems" .)