Hold it, canon! (7)

I believe the answer is:

contain

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'hold' is the definition.
(I know that hold can be written as contain)

'it canon' is the wordplay.
'it canon' anagrams to 'CONTAIN'.
Though, I am not clear how this is indicated.

Can you help me to learn more?

(Other definitions for contain that I've seen before include "I cannot (anag) - hold back" , "Include - restrict" , "Keep the lid on" , "Carry" , "keep within bounds" .)

I've seen this clue in The Irish News.

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