A prescribed selection of foods (4)
I believe the answer is:
diet
'a prescribed selection of foods' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for diet that I've seen before include "Prescribed food - council" , "regular intake" , "Legislative assembly in some countries" , "Restrict food-intake" , "(Perhaps, try to) reduce rump; parliament" .)