Definition of clarts:
(n) :
(now Scotland, Northern England) Sticky mud, mire or filth.
(v) :
(transitive, now Scotland, Northern England) To daub, smear, or spread, especially with mud, etc.; to dirty.
(n) :
A daub.
(n) :
Unwanted stuff; junk; clutter; rubbish; stuff that is in the way.
(n) :
(Geordie, derogatory) A person who is unclean.
(n) :
(Geordie, derogatory) A fool.