What one eats, stoned on marijuana (4,3)
I believe the answer is:
high tea
'what one eats' is the definition.
(type of meal)
'stoned on marijuana' is the wordplay.
'stoned' becomes 'high' (both can mean under the influence of drugs).
'on' means one lot of letters go next to another.
'marijuana' becomes 'tea' (slang term for the drug).
'high'+'tea'='HIGH TEA'
(Other definitions for high tea that I've seen before include "A lofty kind of evening meal" , "Early evening meal" , "Early-evening meal" , "Late afternoon meal which includes a cooked dish" , "Late-afternoon meal" .)