Pop up again (3)

I believe the answer is:

dad

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'pop' is the definition.
(both can mean one's father)

I don't understand the remainder of the clue.

(Other definitions for dad that I've seen before include "Relation" , "Popular and informal father" , "Mum's mate" , "Pa" , "Father, in short" .)

I've seen this clue in the Evening Standard.

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