In the neighbourhood restaurant - the ultimate secret (6)
I believe the answer is:
closet
'secret' is the definition.
('closet' can be a synonym of 'secret')
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for closet that I've seen before include "Cupboard (to come out of)" , "A small room - best to come out of it" , "Covert" , "Small room or wardrobe" , "A small room - secret?" .)