Within brief time after whiskey's gone, pass over large cocktail (3,7)
I believe the answer is:
tom collins
'cocktail' is the definition.
(Tom Collins is a cocktail)
'within brief time after whiskey's gone pass over large' is the wordplay.
I cannot really understand how this works, but
'within' could be 'in' and 'in' is located in the answer.
'time' could be 't' (abbreviation) and 't' is found in the answer.
'pass' could be 'col' (col is a term for a mountain pass) and 'col' is present in the answer.
'over' could be 'o' (cricket abbreviation) and 'o' is found in the answer.
'large' could be 'l' (eg in clothes sizes) and 'l' is found within the answer.
The remaining letters 'ms' 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?
(Other definitions for tom collins that I've seen before include "Long iced drink of gin, lemon juice and soda water" , "Gin makes this" , "Gin-based cocktail" , "Cocktail using gin" .)