Was finished, in the past, as a pudding ingredient (4)
I believe the answer is:
sago
'a pudding ingredient' is the definition.
(I've seen this in another clue)
'was finished in the past' is the wordplay.
I cannot really see how this works, but
'past' could be 'ago' (similar in meaning) and 'ago' is present in the answer.
A single letter 's' remains which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
'as' is the link.
Can you help me to learn more?
(Other definitions for sago that I've seen before include "dessert?" , "Starchy cereal used in puddings" , "Powdery starch from a palm" , "Starchy pudding cereal" , "Starchy foodstuff" .)