Cleaners frighten off toffs (10)
I believe the answer is:
detergents
'cleaners' is the definition.
(detergent is a kind of cleaner)
'frighten off toffs' is the wordplay.
'frighten off' becomes 'deter' (I've seen this in another clue).
'toffs' becomes 'gents' (gentlemen - toff can mean an upper-class person).
'deter'+'gents'='DETERGENTS'
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