Crossword Genius

Trained spies prove to be overpowering (10)

Ross

I believe the answer is:

oppressive

'be overpowering' is the definition.
(thesaurus)

'trained spies prove' is the wordplay.
'trained' indicates an anagram (to train can mean to grow something into a shape).
'spies'+'prove'='spiesprove'
'spiesprove' with letters rearranged gives 'OPPRESSIVE'.

'to' is the link.

(Other definitions for oppressive that I've seen before include "cruel" , "overpowering!" , "Tyrannical" , "Harsh, authoritarian" , "Sultry" .)

I've seen this clue in The Telegraph.
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