Intense egghead to leave substitute, shortly (3)

I believe the answer is:

dep

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'substitute shortly' is the definition.
I know nothing about this answer so I can't tell whether it can be defined by this definition.

'intense egghead to leave' is the wordplay.
'intense' becomes 'deep' (associated in meaning).
'egghead' becomes 'e' (head letter of 'egg').
'to leave' suggests deleting specific letters.
'deep' with 'e' taken away is 'DEP'.

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I've seen this clue in The Irish Times.

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