Rugby supporter keeps providing backing for lout (7)
I believe the answer is:
ruffian
'lout' is the definition.
(I've seen this before)
'rugby supporter keeps providing backing' is the wordplay.
'rugby' becomes 'RU'.
'supporter' becomes 'fan' (fan is a kind of supporter).
'keeps' means one lot of letters goes inside another.
'providing' becomes 'if' (eg 'providing it's sunny' means 'if it's sunny').
'backing' shows that the letters should be reversed in order.
'if' in reverse letter order is 'fi'.
'fan' enclosing 'fi' is 'ffian'.
'ru'+'ffian'='RUFFIAN'
'for' acts as a link.
(Other definitions for ruffian that I've seen before include "Bully" , "Violent, lawless person" , "Rowdy" , "Aggressive, rude troublemaker" , "Lout" .)