Passion of republic once ousting English (3)
I believe the answer is:
ire
'passion of republic' is the definition.
'ire' can be an answer for 'passion' (I've seen this before). I'm not sure about the 'of republic' bit.
'once ousting english' is the wordplay.
'once ousting' becomes 'ir' (I can't explain this - if you can you should believe this answer much more).
'english' becomes 'e' (abbreviation).
'ir'+'e'='IRE'
(Other definitions for ire that I've seen before include "Strong feeling" , "Losing head" , "Irritation, anger" , "Choler" , "Strong emotion" .)