Lincoln’s assassin, by front of stage, stalls (6)
I believe the answer is:
booths
'stalls' is the definition.
('booth' can be a synonym of 'stall')
'lincoln's assassin by front of stage' is the wordplay.
'lincoln's assassin' becomes 'Booth' (John Wilkes Booth shot Abraham Lincoln).
'by' is a charade indicator (letters next to each other).
'front of' says to take the initial letters.
The initial letter of 'stage' is 's'.
'booth'+'s'='BOOTHS'
(Other definitions for booths that I've seen before include "Small areas, for voting say" , "Small area, for voting say" , "Small temporary shops, at a market say" , "Small shops, at a fair say" , "Small temporary stalls, for voting, say" .)