Regret going in a heartless gaol for 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 one could define the other.
'regret going in a heartless gaol' is the wordplay.
'regret' becomes 'rue' (synonyms).
'going in' is an insertion indicator.
'a heartless' says to hollow out the word (remove centre letters).
'gaol' with its middle removed is 'gl'.
'rue' placed into 'gl' is 'GRUEL'.
'for' is the link.
Can you help me to learn more?
(Other definitions for gruel that I've seen before include "Luger (anag)" , "Thin liquid food" , "Unappetising food" , "Thin porridge" , "sloppy fare" .)