Knock down boyfriend at front of ship (4,4)
I believe the answer is:
bowl over
'knock down' is the definition.
(both can mean to topple)
'boyfriend at front of ship' is the wordplay.
'boyfriend' becomes 'lover' (boyfriend is a type of lover).
'at' says to put letters next to each other (I've seen this in other clues).
'front of ship' becomes 'bow' (term for the front of a ship).
'lover' after 'bow' is 'BOWL OVER'.
(Other definitions for bowl over that I've seen before include "Overwhelm with surprise or emotion - at cricket?" , "Knock down" , "wow" , "Slay" , "really impress" .)