Condition of small gallery (5)
I believe the answer is:
state
'condition' is the definition.
(I've seen this before)
'small gallery' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'gallery' becomes 'tate' (I've seen this before).
's'+'tate'='STATE'
'of' is the link.
(Other definitions for state that I've seen before include "Georgia < or Virginia" , "Declare; affirm" , "whole people" , "eg Iowa" , "Declare: condition" .)