Agreement entered securing deal (7)
I believe the answer is:
entente
'deal' is the definition.
(entente is an alliance or agreement)
'agreement entered securing' is the wordplay.
'securing' says the answer is hidden in the clue.
'ENTENTE' can be found hidden inside 'agreement entered'.
(Other definitions for entente that I've seen before include "Harmony" , "Political agreement" , "that brings nations closer together" , "Interstate understanding" , "Diplomatic agreement" .)