Awful old Democrat, one old American (6)
I believe the answer is:
odious
'awful' is the definition.
(I've seen this in another clue)
'old democrat one old american' is the wordplay.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'democrat' becomes 'd'.
'one' becomes 'i' (Roman numeral).
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'american' becomes 'US' (United States).
'o'+'d'+'i'+'o'+'us'='ODIOUS'
(Other definitions for odious that I've seen before include "Loathsome and repugnant" , "Really hateful, detestable" , "Thoroughly obnoxious, hateful" , "Abominable, detestable" , "Unpleasant, repulsive" .)