Crossword Genius

Bad user, for certain (4)

Ross

I believe the answer is:

sure

'certain' is the definition.
(synonyms)

'bad user' is the wordplay.
'bad' indicates an anagram.
'user' is an anagram of 'SURE'.

'for' acts as a link.

(Other definitions for sure that I've seen before include "of course" , "certainly in the USA" , "Undoubtedly true" , "Feeling no doubt" , "Convinced" .)

I've seen this clue in the Evening Standard.
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