Is youngster up to finding restaurant? (7)
I believe the answer is:
canteen
'restaurant?' is the definition.
(both can mean somewhere to eat)
'is youngster up to' is the wordplay.
I cannot really see how this works, but
'youngster' could be 'teen' (I've seen this in another clue) and 'teen' is located in the answer.
The remaining letters 'can' is a valid word which might be clued in a way I don't see.
This may be the basis of clue (or it may be nonsense).
'finding' is the link.
(Other definitions for canteen that I've seen before include "Office eating area" , "Soldier's water-flask" , "Water or cutlery container" , "Workplace restaurant" , "Cafe, flask and cutlery box" .)