Say Dorothy's served up heavy food (6)
I believe the answer is:
stodge
'heavy food' is the definition.
(I've seen this before)
'say dorothy's served up' is the wordplay.
'say' becomes 'eg' (both can mean for example).
'dorothy's' becomes 'dot's' (short for Dorothy).
'served up' is a reversal indicator (in a down clue, going upwards).
'eg'+'dots'='egdots'
'egdots' backwards is 'STODGE'.
(Other definitions for stodge that I've seen before include "Heavy filling food" , "'Heavy, starchy food (6)'" , "Heavy, often starchy, food" , "heavy fare" , "Heavy and indigestible food" .)