Only half of it is in the bag, but there's plenty (5)

I believe the answer is:

stack

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'plenty' is the definition.
(I know that plenty can be written as stack)

'only half of it is in the bag but' is the wordplay.
'only half of' indicates taking half.
'is in the' is an insertion indicator.
'bag but' becomes 'sack' (both can mean a container. I am not sure about the 'but' bit.).
'it' halved is 't'.
't' inserted into 'sack' is 'STACK'.

'there's' is the link.

Can you help me to learn more?

(Other definitions for stack that I've seen before include "A lot" , "Tall chimney" , "Aggregation or heap" , "Pile of hay" , "functioned successfully in Scotland" .)

I've seen this clue in the Evening Standard.

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