Crossword Genius

Plenty backing person that's unpleasant (6)

Ross

I believe the answer is:

enough

'plenty' is the definition.
(synonyms)

'backing person that's unpleasant' is the wordplay.
'backing' is a reversal indicator.
'person' becomes 'one' ('one' can mean an unspecified person).
'that's unpleasant' becomes 'ugh' (expression of disgust).
'one' reversed gives 'eno'.
'eno'+'ugh'='ENOUGH'

(Other definitions for enough that I've seen before include "As much as desirable" , "To the required degree" , "The quantity needed, sufficient" , "satisfying" , "Adequate amount to meet the purpose" .)

I've seen this clue in The Telegraph.
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