Turn right before old gallery (6)
I believe the answer is:
rotate
'turn' is the definition.
(rotating is a kind of turning)
'right before old gallery' is the wordplay.
'right' becomes 'r' (common abbreviation).
'before' is a charade indicator (letters next to each other).
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'gallery' becomes 'tate' (I've seen this before).
'r'+'o'+'tate'='ROTATE'
(Other definitions for rotate that I've seen before include "Move round centre" , "Go round and round" , "Whisk round" , "Alternate" , "Spin as on axle" .)