Right to support the Queen (6)
I believe the answer is:
proper
'right' is the definition.
(synonyms)
'support the queen' is the wordplay.
'support' becomes 'prop' (prop up can mean to support).
'the queen' becomes 'ER' (abbreviation for Elizabeth Regina).
'prop'+'er'='PROPER'
'to' acts as a link.
(Other definitions for proper that I've seen before include "part of Mass" , "Right, correct or appropriate" , "Genuine; respectable" , "Appropiate, right" , "Correct; respectable" .)