Crossword Genius

Spy a toff (5)

Ross

I believe the answer is:

agent

'spy' is the definition.
(thesaurus)

'a toff' is the wordplay.
'toff' becomes 'gent' (I've seen this in other clues).
'a'+'gent'='AGENT'

(Other definitions for agent that I've seen before include "Delegate" , "One may be working" , "Vehicle" , "Author" , "Catalyst" .)

I've seen this clue in The Telegraph.
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