Polish side's first fans (5)
I believe the answer is:
buffs
'fans' is the definition.
('buff' can be a synonym of 'fan')
'polish side's first' is the wordplay.
'polish' becomes 'buff' (buffing is a kind of polishing).
'first' indicates taking the first letters.
The initial letter of 'sides' is 's'.
'buff'+'s'='BUFFS'
(Other definitions for buffs that I've seen before include "Experts" , "Enthusiasts" , "Aficionados" .)