Sword needs point to slash (4)
I believe the answer is:
epee
'sword' is the definition.
(sword used in fencing)
'point to slash' is the wordplay.
'point' becomes 'E' (compass point).
'to slash' becomes 'pee' (both can informally mean to urinate).
'e'+'pee'='EPEE'
'needs' acts as a link.
(Other definitions for epee that I've seen before include "there's a point to it" , "Another fencing sword" , "Rapier" , "Fencer's weapon" , "Duelling weapon" .)