Screen in restaurant on base (6)
I believe the answer is:
grille
'screen' is the definition.
(screen of bars which can be looked through)
'restaurant on base' is the wordplay.
'restaurant' becomes 'grill' (grill is a kind of restaurant).
'on' is a charade indicator (letters next to each other).
'base' becomes 'e' (Euler's number - base of natural logarithms).
'grill'+'e'='GRILLE'
'in' acts as a link.
(Other definitions for grille that I've seen before include "It affords ventilation" , "Metal lattice-work" , "Partition" , "Part of an air-cooling system" , "Grating, metal screen" .)