Scottish footballers once with demand for unrestrained expenditure (7)
I believe the answer is:
splurge
'unrestrained expenditure' is the definition.
'scottish footballers once with demand' is the wordplay.
'scottish footballers once' becomes 'spl' (Scottish Premier League).
'with' means one lot of letters go next to another.
'demand' becomes 'urge'.
'spl'+'urge'='SPLURGE'
'for' acts as a link.
(Other definitions for splurge that I've seen before include "Spend money freely, be extravagant" , "Bout of extravagant spending" , "Immoderate indulgence" , "Squander" , "lashing out" .)