Young agent, not entirely free to speak? (5)
I believe the answer is:
ungag
'free to speak?' is the definition.
(as in removing a gag on someone)
'young agent not entirely' is the wordplay.
'not entirely' says the answer is hidden in the clue.
'UNGAG' is hidden in the letters of 'young agent'.
(Other definitions for ungag that I've seen before include "free to talk" , "Free to communicate" , "Remove ban on free speech" .)