Betray in hush-hush operation (4)
I believe the answer is:
shop
'betray' is the definition.
(thesaurus)
'in hush-hush operation' is the wordplay.
'in' says the answer is hidden in the clue.
'SHOP' can be found hidden inside 'hush hush operation'.
(Other definitions for shop that I've seen before include "Retail outlet" , "Sell" , "Give away" , "Be disloyal to" , "Place to buy" .)