When King & Lewis electrified segregated Selma, initially lacking appreciation (9)
I believe the answer is:
thankless
'lacking appreciation' is the definition.
'when king lewis electrified segregated selma initially' is the wordplay.
'when' becomes 'than' ('than' can mean 'when' in some constructions).
'initially' suggests taking the first letters.
The initial letters of 'king lewis electrified segregated selma' is 'kless'.
'than'+'kless'='THANKLESS'
(Other definitions for thankless that I've seen before include "Showing no gratitude" , "Unappreciated" , "Receiving no appreciation" .)