Defeat wife going on about steering apparatus (9)
I believe the answer is:
overwhelm
'defeat' is the definition.
(I know that overwhelm is a more specific form of the action beat)
'wife going on about steering apparatus' is the wordplay.
'wife' becomes 'w' (abbreviation).
'going on' means one lot of letters go next to another.
'about' becomes 'over' (both can mean around).
'steering apparatus' becomes 'helm' (as in the helm on a boat).
'w' put after 'over' is 'overw'.
'overw'+'helm'='OVERWHELM'
(Other definitions for overwhelm that I've seen before include "Vanquish" , "Swamp - have a strong emotional effect on" , "Overcome by superior force" , "Snow under" , "Submerge" .)