Enter picture books into soup packet (9)

I believe the answer is:

photobomb

I'm a little stuck... Click here to teach me more about this clue!

'enter picture' is the definition.
I know nothing about this answer so I can't judge whether this works.

'books into soup packet' is the wordplay.
'books' becomes 'OT' (Old Testament).
'into' means one lot of letters goes inside another.
'soup' becomes 'pho' (type of Vietnamese soup).
'packet' becomes 'bomb' (I've seen this before).
'ot' going inside 'pho' is 'photo'.
'photo'+'bomb'='PHOTOBOMB'

Can you help me to learn more?

I've seen this clue in The Independent.

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