A left-winger kept outside party much admired (6)
I believe the answer is:
adored
'much admired' is the definition.
'a left-winger kept outside party' is the wordplay.
'left-winger' becomes 'red' (red is a kind of left-winger).
'kept outside' means one lot of letters goes inside another.
'party' becomes 'do' (do is a kind of party).
'a'+'red'='ared'
'ared' enclosing 'do' is 'ADORED'.
(Other definitions for adored that I've seen before include "Loved intensely" , "having lover" , "Worshipped and venerated" , "Worshipped, loved" , "Loved dearly" .)