A wise guy alone with a Scotsman (7)
I believe the answer is:
solomon
'a wise guy' is the definition.
(I've seen this before)
'alone with a scotsman' is the wordplay.
'alone' becomes 'solo' (as in a musical solo).
'with' says to put letters next to each other.
'a scotsman' becomes 'mon'.
'solo'+'mon'='SOLOMON'
(Other definitions for solomon that I've seen before include "Biblical wise king" , "wise guy" , "Wise old king of Israel" , "OT king" , "Proverbially wise king" .)