The heartless part of school dance shouldn't last long (6)

I believe the answer is:

protem

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'shouldn't last long' is the definition.
I don't know anything about this answer so I cannot tell whether it can be defined by this definition.

'the heartless part of school dance' is the wordplay.
'heartless' says to hollow out the word (remove centre letters).
'part of' is an insertion indicator (part of the inside).
'school dance' becomes 'prom' (I've seen this in another clue).
'the' with its centre taken out is 'te'.
'te' put into 'prom' is 'PROTEM'.

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I've seen this clue in The Irish Times.

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