Queen cross over East wing (6)
I believe the answer is:
annexe
'wing' is the definition.
('annexe' can be a synonym of 'wing')
'queen cross over east' is the wordplay.
'queen' becomes 'anne' (I've seen this before**).
'cross' becomes 'x'.
'over' is a charade indicator (letters next to each other).
'east' becomes 'e' ('E' can be a synonym of 'east').
'anne'+'x'+'e'='ANNEXE'
(Other definitions for annexe that I've seen before include "outbuilding" , "Added section of document" , "extra space" , "Side building" , "Extra piece of building" .)