Collar Scotsman, hooligan ... (7)
I believe the answer is:
ruffian
'hooligan' is the definition.
(I know that hooligan can be written as ruffian)
'collar scotsman' is the wordplay.
'collar' becomes 'ruff' (ruff is a kind of collar).
'scotsman' becomes 'ian' (common Scottish name).
'ruff'+'ian'='RUFFIAN'
(Other definitions for ruffian that I've seen before include "Bully" , "Rowdy" , "Violent, lawless person" , "Rude fellow" , "Funfair (anag)" .)