Go over part of East End showing weapon (8)
I believe the answer is:
crossbow
'weapon' is the definition.
(crossbow is a kind of weapon)
'go over part of east end' is the wordplay.
'go over' becomes 'cross' (to cross over).
'part of east end' becomes 'Bow' (area of East London).
'cross'+'bow'='CROSSBOW'
'showing' is the link.
(Other definitions for crossbow that I've seen before include "Missile-launcher" , "Weapon (used to set off a quarrel?)" , "historic weapon" , "One responsible for shooting bolts" , "Old weapon of war" .)