Cocktail for a fellow-traveller (7)
I believe the answer is:
sidecar
'cocktail' is the definition.
(I know that Sidecar is a type of cocktail)
'a fellow-traveller' is the wordplay.
I cannot really understand how this works, but
'a' is found in the answer.
'fellow' could be 'sid' (Sid is a man's name) and 'sid' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
'for' acts as a link.
Can you help me to learn more?
(Other definitions for sidecar that I've seen before include "that biker may take with him" , "Attachment on motorcycle to carry passenger" , "passenger compartment" , "In which a passenger may be taken" , "Cocktail; bike attachment" .)