Hush-hush (6)
'hush-hush' is the definition.
(synonyms)
This is the entire clue.
(Other definitions for secret that I've seen before include "Unidentified" , "'Hidden, covert (6)'" , "Inner" , "Security marking" , "Confidence" .)
'hush-hush' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for top secret that I've seen before include "As Bond mission" , "label on some classified documents" , "the knack of sleeping well?" , "Highly classified" , "As 007 mission" .)