Nonsense! The twit must relinquish it and go off (7)
I believe the answer is:
twaddle
'nonsense' is the definition.
(informal term for nonsense or rubbish)
'twit must relinquish it and go off' is the wordplay.
'must relinquish' is a deletion indicator.
'and' is a charade indicator (letters next to each other).
'go off' becomes 'addle' (eg an egg might addle).
'twit' with 'it' taken away is 'tw'.
'tw'+'addle'='TWADDLE'
'the' acts as a link.
(Other definitions for twaddle that I've seen before include "Poppycock" , "bunk" , "Moonshine" , "Hot air" , "Foolish words" .)