Said a starter will do - or a pudding (4)

I believe the answer is:

sago

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'a pudding' is the definition.
(I've seen this before)

'said a starter will do' is the wordplay.
'a starter' says to take the initial letters.
'will do' becomes 'ago' (I am not sure about this - if you are sure you should believe this answer much more).
The initial letter of 'said' is 's'.
's'+'ago'='SAGO'

'or' is the link.

Can you help me to learn more?

(Other definitions for sago that I've seen before include "Edible powdery starch" , "Cereal, used in pudding" , "Powdery starchy food" , "Starchy grain used in desserts" , "Starchy cereal used in puddings" .)

I've seen this clue in the Evening Standard.

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