Shoot dead leaders in rally at Lusaka (7)
I believe the answer is:
lateral
'shoot' is the definition.
(I've seen this before)
'dead leaders in rally at lusaka' is the wordplay.
'dead' becomes 'late' ('late' can be similar in meaning to 'dead').
'leaders in' suggests taking the first letters.
The first letters of 'rally at lusaka' is 'ral'.
'late'+'ral'='LATERAL'
(Other definitions for lateral that I've seen before include "to one side" , "Tall ear (anag.)" , "Way of thinking" , "Towards the side" , "Side branch" .)