Scared, drunk, having one cocktail (7)
I believe the answer is:
sidecar
'cocktail' is the definition.
(I know that Sidecar is a type of cocktail)
'scared drunk having one' is the wordplay.
'drunk' indicates anagramming the letters.
'having' indicates putting letters inside.
'one' becomes 'i' (Roman numeral).
'scared' anagrammed gives 'sdecar'.
'sdecar' going around 'i' is 'SIDECAR'.
(Other definitions for sidecar that I've seen before include "Vehicle" , "Where a passenger may go" , "Attachment to motorcycle to accommodate passenger" , "Low-slung two-wheeler" , "In which Gromit goes" .)