Supporting Democrat as president (4)
I believe the answer is:
ford
'president' is the definition.
(Gerald Ford)
'supporting democrat' is the wordplay.
'supporting' becomes 'for' ().
'democrat' becomes 'd'.
'for'+'d'='FORD'
'as' acts as a link.
(Other definitions for ford that I've seen before include "way for pedestrians" , "Shallow part of stream to cross" , "Shallow place for river crossing" , "38th US president, Gerald" , "Shallow river-crossing" .)