Pudding originally standard in the past (4)
I believe the answer is:
sago
'pudding' is the definition.
(I've seen this before)
'originally standard in the past' is the wordplay.
'originally' suggests taking the first letters.
'in the past' becomes 'ago' (three years ago means three years in the past).
The first letter of 'standard' is 's'.
's'+'ago'='SAGO'
(Other definitions for sago that I've seen before include "Starchy foodstuff" , "Starchy grain used in desserts" , "dessert?" , "Powdery starch from a palm" , "Palm cereal" .)