Nationalist at uprising after start of parade (7)
I believe the answer is:
patriot
'nationalist' is the definition.
('patriot' can be a synonym of 'nationalist')
'at uprising after start of parade' is the wordplay.
'uprising' becomes 'riot' (I've seen this before**).
'after' is a charade indicator (letters next to each other).
'start of' indicates taking the first letters.
The initial letter of 'parade' is 'p'.
'at'+'riot'='atriot'
'atriot' put after 'p' is 'PATRIOT'.
(Other definitions for patriot that I've seen before include "Flag waver" , "Loyal citizen" , "One supporting country" , "Country lover" , "Country-lover" .)