Base supporting Democrat in county town (7)
I believe the answer is:
bedford
'county town' is the definition.
(county town of Bedfordshire)
'base supporting democrat' is the wordplay.
'base' becomes 'bed' (both can mean the bottom of something).
'supporting' becomes 'for' (being for something means supporting it).
'democrat' becomes 'd'.
'bed'+'for'+'d'='BEDFORD'
'in' is the link.
(Other definitions for bedford that I've seen before include "English county town" , "County town to north of London" .)