Sailor on street to attack with knife (4)
I believe the answer is:
stab
'attack with knife' is the definition.
(to stab is to attack with a blade)
'sailor on street' is the wordplay.
'sailor' becomes 'ab' (abbreviation for able seaman).
'on' says to put letters next to each other.
'street' becomes 'st' (abbreviation).
'ab' put after 'st' is 'STAB'.
'to' is the link.
(Other definitions for stab that I've seen before include "Jab" , "Twinge; guess" , "Injure with knife" , "Wound with blade" , "It could be the death of you" .)