Face Lincoln as a former leader (6)
I believe the answer is:
mugabe
'a former leader' is the definition.
(Robert Mugabe, former leader of Zimbabwe)
'face lincoln' is the wordplay.
'face' becomes 'mug' (informal term for face).
'lincoln' becomes 'abe' (Abraham Lincoln).
'mug'+'abe'='MUGABE'
'as' is the link.
(Other definitions for mugabe that I've seen before include "Zimbabwean leader" , "Zimbabwe's president since 1987" , "ZANU-PF leader" , "African politician" , "Mnangagwa's predecessor" .)