Debauchee's son, Irish, can start to swim in two rivers (3,4,8)
I believe the answer is:
sir john falstaff
'debauchee's' is the definition.
(debauched Shakespeare character)
'son irish can start to swim in two rivers' is the wordplay.
I cannot quite understand how this works, but
'son' could be 's' (genealogical abbreviation for son) and 's' is found within the answer.
'irish' could be 'ir' (abbreviation) and 'ir' is found within the answer.
'can' could be 'john' (slang for toilet) and 'john' is present in the answer.
The remaining letters 'falstaff' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Another definition for sir john falstaff that I've seen is " As cowardly soldier".)