Who's not to be trusted, nastier than rascal? (10)

I believe the answer is:

charlatans

'who's not to be trusted' is the definition.

'nastier than rascal?' is the wordplay.
'nastier' is an anagram indicator (I've seen 'nasty' mean this (a nasty or wrong spelling)).
'than'+'rascal'='thanrascal'
'thanrascal' with letters rearranged gives 'CHARLATANS'.

(Another definition for charlatans that I've seen is " Fakes".)

I've seen this clue in The Everyman puzzle in The Observer.

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