Tradition supported by the Queen as patron (8)
I believe the answer is:
customer
'patron' is the definition.
(I've seen this before)
'tradition supported by the queen' is the wordplay.
'tradition' becomes 'custom' ('custom' can be a synonym of 'tradition').
'supported by' is a charade indicator (letters next to each other) (letters go below - in down clue).
'the queen' becomes 'er' (Elizabeth Regina).
'custom'+'er'='CUSTOMER'
'as' acts as a link.
(Other definitions for customer that I've seen before include "Shopper (or now rail passenger!)" , "Shop client" , "One who buys goods or services" , "Rail passenger, nowadays" , "Someone who pays for goods or services" .)