Call to bring in a half-time recap? (9)

I believe the answer is:

summation

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'call' is the definition.
The answer and definition can be both acts as well as being singular nouns.
Maybe there's an association between them I don't understand?

'to bring in a half-time recap?' is the wordplay.
'to bring in' indicates putting letters inside.
'half' suggests halving the letters.
'recap?' becomes 'summon' (I can't explain this - if you can you should give a lot more credence to this answer).
'time' halved is 'ti'.
'a'+'ti'='ati'
'ati' inserted inside 'summon' is 'SUMMATION'.

Can you help me to learn more?

(Other definitions for summation that I've seen before include "Adding process" , "Synopsis" .)

I've seen this clue in The Independent.

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