Republican in a party, fit and winning (8)
I believe the answer is:
adorable
'winning' is the definition.
(I've seen this before)
'republican in a party fit' is the wordplay.
'republican' becomes 'r' (abbreviation).
'in' is an insertion indicator.
'party' becomes 'do' (do is a kind of party).
'fit' becomes 'able' (similar in meaning).
'a'+'do'+'able'='adoable'
'r' put within 'adoable' is 'ADORABLE'.
'and' acts as a link.
(Other definitions for adorable that I've seen before include "'Lovable, delightful (8)'" , "Lovely and attractive" , "Winsome" , "winning" , "Cute and cuddly?" .)