In advance, dish out jam (8)
I believe the answer is:
preserve
'jam' is the definition.
(I've seen this before)
'in advance dish out' is the wordplay.
'in advance' becomes 'pre' (prefix meaning 'before').
'dish out' becomes 'serve' (as in dishing out food).
'pre'+'serve'='PRESERVE'
(Other definitions for preserve that I've seen before include "Toast option" , "Maintain - jam" , "Keep from decay, corpse or food" , "Area of activity" , "Keep safe from spoilage" .)