Leak classified intelligence finally (7)
I believe the answer is:
secrete
'leak' is the definition.
(thesaurus)
'classified intelligence finally' is the wordplay.
'classified' becomes 'secret' ('secret' can be similar in meaning to 'classified').
'finally' says to take the final letters.
The last letter of 'intelligence' is 'e'.
'secret'+'e'='SECRETE'
(Other definitions for secrete that I've seen before include "Form substance for use within body, as liver does bile" , "Hide; as gland does" , "Hold and send out substance into the body as gland does" , "Place out of sight, hide" , "Release bodily fluid" .)