Caledonian boozer tours clubs (4)
I believe the answer is:
scot
'caledonian' is the definition.
(I've seen this before)
'boozer tours clubs' is the wordplay.
'boozer' becomes 'sot' (I've seen this in other clues).
'tours' means one lot of letters goes inside another (to tour can mean to go around).
'clubs' becomes 'c' (abbreviation used in card games such as bridge).
'sot' going around 'c' is 'SCOT'.
(Other definitions for scot that I've seen before include "one from the North of Britain" , "Someone from Dundee?" , "Highlander, say" , "9 [KEIR HARDIE], say" , "Eg, a Glaswegian" .)