Spellbound, inclined to support Republican (4)
I believe the answer is:
rapt
'spellbound' is the definition.
(thesaurus)
'inclined to support republican' is the wordplay.
'inclined' becomes 'apt' ('apt' can be similar in meaning to 'inclined').
'to support' is a charade indicator (letters next to each other) (in a down clue, some letters hold others up).
'republican' becomes 'r' (abbreviation).
'apt' after 'r' is 'RAPT'.
(Other definitions for rapt that I've seen before include "Ecstatic - engrossed" , "Enchanted in part" , "Engrossed, spellbound" , "Enthralled, captivated" , "Ecstatic in part" .)