Emit gas and perhaps smoke around gallery (8)
I believe the answer is:
eructate
'emit gas' is the definition.
(to eructate is to burp or belch)
'perhaps smoke around gallery' is the wordplay.
'perhaps smoke' becomes 'cure' (as in cured meats).
'around' says the letters should be written backwards.
'gallery' becomes 'tate' (Tate Modern, Tate Britain etc).
'cure' reversed gives 'eruc'.
'eruc'+'tate'='ERUCTATE'
'and' acts as a link.
(Other definitions for eructate that I've seen before include "Tea cruet made one to belch" , "Belch during tea truce" , "Belch following tea cruet" .)