Seafood left by Scotsman having a ball, note (9)

I believe the answer is:
langouste
'seafood' is the definition.
(langouste is a kind of seafood)
'left by scotsman having a ball note' is the wordplay.
I cannot quite see how this works, but
'left' could be 'l' (common abbreviation) and 'l' is found in the answer.
'a' could be 'an' and 'an' is found within the answer.
'ball' could be 'o' (O looks like a ball) and 'o' is located in the answer.
'note' could be 'te' (musical note as in do re mi fa so la ti) and 'te' is found in the answer.
The remaining letters 'gus' 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?
(Other definitions for langouste that I've seen before include "something to eat" , "Sea creature" , "thing to devour!" , "Swimmer" , "It may be eaten roasted" .)
