Small inexpensive restaurant (6)
I believe the answer is:
bistro
'small inexpensive restaurant' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for bistro that I've seen before include "Coming out of restaurant" , "'Small, inexpensive restaurant (6)'" , "Small informal French restaurant" , "Small bar-cum-restaurant" , "Cheap restaurant" .)