Could he serve you a line in cheap drink? (6)
I believe the answer is:
waiter
'could he serve you a line in cheap drink?' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'could he' is the wordplay.
I cannot really see how this works, but
'he' could be 'waite' and 'waite' is found within the answer.
A single letter 'r' remains 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 waiter that I've seen before include "Herr Ober (Ger.)" , "Restaurant employee" , "One paid to serve" , "Restaurant worker" , "Estragon or Vladimir, for example" .)