Socialist to abandon Worcestershire seat (8)
I believe the answer is:
redditch
'worcestershire seat' is the definition.
(parliamentary constituency in Worcestershire)
'socialist to abandon' is the wordplay.
'socialist' becomes 'red' (socialism is often associated with the colour red).
'to abandon' becomes 'ditch' (ditching is a kind of abandoning).
'red'+'ditch'='REDDITCH'
(Other definitions for redditch that I've seen before include "Town S. of Birmingham; CD dither (anag.)" , "Worcestershire new town" , "English town" , "Midlands settlement" .)