How trapdoor victim is not coming to fruition? (7,7)

I believe the answer is:

falling through

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'how trapdoor victim is not' is the definition.
I can't judge whether this defines the answer.

'coming to fruition?' is the wordplay.
'coming' becomes 'falling' ('fall' can be a synonym of 'come').
'to fruition?' becomes 'through' (I can't justify this - if you can you should believe this answer much more).
'falling'+'through'='FALLING THROUGH'

Can you help me to learn more?

(Other definitions for falling through that I've seen before include "Failing" , "You wouldn't want it to happen on ice" .)

I've seen this clue in the Sydney Morning Herald.

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