British getting 'nul points', dammit (5)
I believe the answer is:
blast
'dammit' is the definition.
(both are mild expletives)
'british getting nul points' is the wordplay.
'british' becomes 'b' (abbreviation e.g. in 'BBC').
'getting' is a charade indicator (letters next to each other).
'nul points' becomes 'last' (zero points - famously in Eurovision Song Contest).
'b'+'last'='BLAST'
(Other definitions for blast that I've seen before include "slate" , "Severe reprimand; strong gust" , "Mild expletive - sharp explosion" , "Noise of explosion" , "Report" .)