Small cupboard, shut tight, initially (6)
I believe the answer is:
closet
'small cupboard' is the definition.
(I've seen this before)
'shut tight initially' is the wordplay.
'shut' becomes 'close' (synonyms).
'initially' suggests taking the first letters.
The first letter of 'tight' is 't'.
'close'+'t'='CLOSET'
(Other definitions for closet that I've seen before include "small compartment for clothing" , "Cupboard (to come out of)" , "A small room - best to come out of it" , "Small room or wardrobe" , "Private room; cupboard" .)