The fall of General Custer (6)
I believe the answer is:
autumn
'the fall' is the definition.
('autumn' can be a synonym of 'fall')
I can't explain the remainder of the clue.
(Other definitions for autumn that I've seen before include "Season of falling leaves" , "When harvests ripen" , "One of the seasons" , "Harvest season" , "October's season" .)