Weapon's journey north in case of target (7)
I believe the answer is:
trident
'weapon's' is the definition.
(trident is a kind of weapon)
'journey north in case of target' is the wordplay.
'journey' becomes 'ride' (riding is a kind of journeying**).
'north' becomes 'n' ('N' can be a synonym of 'north').
'in' means one lot of letters goes inside another.
'case of' means to remove the middle letters (outsides of).
'target' with its centre removed is 'tt'.
'ride'+'n'='riden'
'riden' going into 'tt' is 'TRIDENT'.
(Other definitions for trident that I've seen before include "Neptune's fork" , "Nuclear missile" , "Submarine-launched ballistic missile" , "Neptune's weapon" , "Weapon on submarine" .)