Small room near front of theatre (6)
I believe the answer is:
closet
'small room' is the definition.
(I've seen this before)
'near front of theatre' is the wordplay.
'near' becomes 'close' (synonyms).
'front of' suggests taking the first letters (the letter at the front of the word).
The initial letter of 'theatre' is 't'.
'close'+'t'='CLOSET'
(Other definitions for closet that I've seen before include "Furtive" , "North American cupboard" , "Covert" , "Small room or cabinet for storage" , "Wardrobe in the US" .)