Fail in court to reveal secret (6)
I believe the answer is:
closet
'secret' is the definition.
(synonyms)
'fail in court' is the wordplay.
'fail' becomes 'lose' (I've seen this in other clues).
'in' is an insertion indicator.
'court' becomes 'ct' (abbreviation used in road names).
'lose' placed within 'ct' is 'CLOSET'.
'to reveal' is the link.
(Other definitions for closet that I've seen before include "American cupboard or wardrobe" , "A small room - best to come out of it" , "place to store gear" , "Furtive" , "Small room or wardrobe" .)