Queen unwell and complaining (7)
I believe the answer is:
railing
'complaining' is the definition.
(railing is a kind of complaining)
'queen unwell' is the wordplay.
'queen' becomes 'r' (r is abbreviation regina. e.g. in ER ).
'unwell' becomes 'ailing' ('ailing' can be a synonym of 'unwell').
'r'+'ailing'='RAILING'
'and' acts as a link.
(Other definitions for railing that I've seen before include "Iron barrier" , "Type of fence - scoffing" , "Gin lair (anag.)" , "barrier appears" , "border of park?" .)