Flailed about having sunk going round lake (10)
I believe the answer is:
floundered
'flailed' is the definition.
Although both the answer and definition are past participle verbs, I can't see how they can define each other.
'about having sunk going round lake' is the wordplay.
I cannot quite see how this works, but
'about' could be 're' ('re' means regarding or about) and 're' is located in the answer.
'round' could be 'o' (round can mean a round object) and 'o' is present in the answer.
'lake' could be 'l' (geographical abbreviation) and 'l' is located in the answer.
The remaining letters 'funded' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Another definition for floundered that I've seen is " Was out of one's depth".)