Extravagant tip a golfer developed (10)
I believe the answer is:
profligate
'extravagant' is the definition.
('profligate' can be a synonym of 'extravagant')
'tip a golfer developed' is the wordplay.
'developed' is an anagram indicator.
'tip'+'a'+'golfer'='tipagolfer'
'tipagolfer' anagrammed gives 'PROFLIGATE'.
(Other definitions for profligate that I've seen before include "Wildly extravagant" , "Dissolute" , "Husband would not be" , "extravagant type" , "Debauched" .)