Apportion a great deal, say (5)

I believe the answer is:

allot

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'apportion' is the definition.
(I know that apportion is a more specific form of allot)

'a great deal say' is the wordplay.
'a great' becomes 'al' (I can't justify this - if you can you should give a lot more credence to this answer).
'deal say' becomes 'lot' (dealing is a kind of lotting).
'al'+'lot'='ALLOT'

Can you help me to learn more?

(Other definitions for allot that I've seen before include "Dispense or distribute" , "deal" , "Parcel out, assign" , "Earmark" , "Hand out" .)

I've seen this clue in The Mirror.

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