The scoundrel with the collar - the Scotsman (7)
I believe the answer is:
ruffian
'the scoundrel' is the definition.
(I've seen this before)
'with the collar the scotsman' is the wordplay.
'with' is a charade indicator (letters next to each other).
'the collar' becomes 'ruff' (ruff is a kind of collar**).
'the scotsman' becomes 'ian'.
'ruff' next to 'ian' is 'RUFFIAN'.
(Other definitions for ruffian that I've seen before include "Rude fellow" , "Hoodlum" , "Rowdy" , "Aggressive, rude troublemaker" , "Yobbo" .)