Weapon from Cuba dumped in narrow street (5)
I believe the answer is:
lance
'weapon' is the definition.
(lance is a kind of weapon)
'cuba dumped in narrow street' is the wordplay.
'cuba' becomes 'c'.
'dumped in' means one lot of letters goes inside another.
'narrow street' becomes 'lane' (I've seen this before).
'c' going inside 'lane' is 'LANCE'.
'from' acts as a link.
(Other definitions for lance that I've seen before include "One like pike" , "Knightly weapon" , "Pointed instrument" , "surgical instrument" , "Incise" .)