See foolish nationalist replacing liberal (7)
I believe the answer is:
witness
'see' is the definition.
('witness' can be a synonym of 'see')
I cannot understand how the rest of the clue works.
(Other definitions for witness that I've seen before include "Testimony - see" , "Bystander" , "Onlooker" , "One giving evidence" , "Evidence, proof" .)