Crush because of ability? (9)
I believe the answer is:
overpower
'crush' is the definition.
(I know this)
'because of ability?' is the wordplay.
'because of' becomes 'over' (eg 'he's upset over it').
'ability?' becomes 'power' ('power' can be a synonym of 'ability').
'over'+'power'='OVERPOWER'
(Other definitions for overpower that I've seen before include "Conquer" , "Subdue - beat" , "Get the better of" , "Subjugate" , "Best" .)