Goes pop over mounting record in engagements (9)

'goes pop over' is the definition.
Although both the answer and definition are verbs in their -s form, I can't understand how one could define the other.

'mounting record in engagements' is the wordplay.
'mounting' shows that the letters should be reversed in order (going up in a down clue).
'record' becomes 'note' (note can mean to record or notate).
'in' means one lot of letters goes inside another.
'engagements' becomes 'dates' ('date' can be a synonym of 'engagement').
'note' backwards is 'eton'.
'eton' going inside 'dates' is 'DETONATES'.

Can you help me to learn more?