Husband follows Queen in museum gallery (8)
I believe the answer is:
verandah
'gallery' is the definition.
('verandah' can be a synonym of 'gallery')
'husband follows queen in museum' is the wordplay.
'husband' becomes 'h'.
'follows' means one lot of letters go next to another.
'queen' becomes 'er' (abbreviation for Elizabeth Regina).
'in' is an insertion indicator.
'museum' becomes 'vanda'.
'er' going inside 'vanda' is 'veranda'.
'h' after 'veranda' is 'VERANDAH'.
(Other definitions for verandah that I've seen before include "Roofed area on the side of a house" , "Roofed platform adjoining a house" , "gallery" , "Porch" , "16 21 [INDIAN IMPORT]" .)