Intelligence agency (6)
'intelligence agency' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for mossad that I've seen before include "Israeli intelligence service" , "Foreign intelligence agency" , "Israeli secret service" , "Israeli intelligence agency" , "Israeli intelligence organisation" .)
(Other definitions for secret service that I've seen before include "Hush-hush organisation" , "Government department involved in espionage" , "MI5 or MI6 (informal)" , "Spies' department" , "Government agency" .)