Arrogant if winning sympathy (6)
I believe the answer is:
uppity
'arrogant' is the definition.
(thesaurus)
'winning sympathy' is the wordplay.
'winning' becomes 'up' (I've seen this in other clues).
'sympathy' becomes 'pity' (pity is a kind of sympathy).
'up'+'pity'='UPPITY'
'if' acts as a link.
(Other definitions for uppity that I've seen before include "Informally presumptuous or self-important" , "Self-important, arrogant" , "Snobbish" , "Pert; haughty" , "In need of slapping down?" .)