Innocent years with vegetarian diet? (5,4)
I believe the answer is:
salad days
'innocent years' is the definition.
The definition suggests a plural noun which matches the answer.
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for salad days that I've seen before include "Time for a vegetarian diet" , "Period of youth and inexperience - on lettuce diet?" , "Carefree youth" , "times when she was young" , "Period of youth and inexperience - ate lettuce dishes?" .)