Posh headgear returned in a state (4)
I believe the answer is:
utah
'a state' is the definition.
(Utah is an example)
'posh headgear returned' is the wordplay.
'posh' becomes 'u' (abbreviation for upper-class - opposite to non-u).
'headgear' becomes 'hat' (hat is a kind of headgear).
'returned' shows that the letters should be reversed in order.
'hat' back-to-front is 'tah'.
'u'+'tah'='UTAH'
'in' is the link.
(Other definitions for utah that I've seen before include "American state, capital Salt Lake City" , "A hut marks the State" , "State of western US" , "Great Salt Lake state" , "Mormon US state" .)