Food for certain days (5)
I believe the answer is:
salad
I believe this clue is a double definition.
'food' is the first definition.
(I know that salad is a type of dish)
'certain days' is the second definition.
(I've seen this in another clue)
'for' acts as a link.
(Other definitions for salad that I've seen before include "One may well be green" , "Raw vegetables, etc" , "healthy food" , "A cold meal with lots of lettuce" , "Raw greens, mainly" .)