Something like skilly, taken as punishment (5)
I believe the answer is:
gruel
'punishment' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for gruel that I've seen before include "sloppy fare" , "Unappetising food" , "Thin soup" , "Luger (anag)" , "cheap fare" .)