Valid snooper at ivermectin stores (9)

I believe the answer is:

operative

'valid' is the definition.
(thesaurus)

'snooper at ivermectin stores' is the wordplay.
'stores' indicates a hidden word.
'OPERATIVE' is hidden in the letters of 'snooper at ivermectin'.

(Other definitions for operative that I've seen before include "American detective" , "Machinist - working" , "Efficient" , "Worker in manufacturing" , "Significant" .)

I've seen this clue in The Independent.

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