Shed tears about principal character of lager lout (4)
I believe the answer is:
Here is my best explanation:
'lout' is the definition.
'shed tears about principal character of lager' is the wordplay.
'shed tears' becomes 'sob'.
'about' means one lot of letters goes inside another.
'principal character of' suggests taking the first letters.
The initial letter of 'lager' is 'l'.
'sob' going around 'l' is 'SLOB'.
(Other definitions for slob that I've seen before include "Sort of ice", "Fat, idle person", "Unattractive person", "Slovenly and unkempt type", "Layabout", "Couch potato", "Boor", "Some sort of ice", "'Slovenly, messy person (4)'" and "Slovenly layabout".)