Never to return wearing dress in theatrical space for visitors (5,4)
I believe the answer is:
green room
'theatrical space for visitors' is the definition.
'never to return wearing dress' is the wordplay.
'never' becomes 'neer' ('ne'er' can be a synonym of 'never').
'to return' is a reversal indicator.
'wearing' means one lot of letters goes inside another.
'dress' becomes 'groom' ('groom' can be a synonym of 'dress'**).
'neer' back-to-front is 'reen'.
'reen' put into 'groom' is 'GREEN-ROOM'.
'in' is the link.
(Other definitions for green room that I've seen before include "Place for actors to relax" , "Where actors can relax in the theatre" , "theatre? Only a bit of it" , "backstage area" , "Here's the rest of the cast" .)