Crossword Genius

"Nonsense!" returned the advisor, "He's a pest" (9)

Ross

I believe the answer is:

tormentor

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'a pest' is the definition.
(thesaurus)

'nonsense returned the advisor he's' is the wordplay.
'nonsense' becomes 'rot' (rot can mean nonsense or rubbish).
'returned' is a reversal indicator.
'the advisor he' becomes 'mentor' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'rot' back-to-front is 'tor'.
'tor'+'mentor'='TORMENTOR'

Can you help me to learn more?

(Other definitions for tormentor that I've seen before include "Who would tease" , "One causes distress" , "One causes pain" , "One giving great pain or annoyance" , "Person causing" .)

I've seen this clue in the Evening Standard.
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