Condition of second gallery (5)
I believe the answer is:
state
'condition' is the definition.
(the state something is in)
'second gallery' is the wordplay.
'second' becomes 's' (common abbreviation).
'gallery' becomes 'tate' (Tate Modern, Tate Britain etc).
's'+'tate'='STATE'
'of' acts as a link.
(Other definitions for state that I've seen before include "Public" , "For example, New York or Washington but not Boston or Philadelphia" , "Pomp; nation" , "See 18" , "A test (anag.)" .)