Piece of good fortune for Democrat involved in victory before autumn (8)
I believe the answer is:
windfall
'piece of good fortune' is the definition.
(I've seen this in another clue)
'democrat involved in victory before autumn' is the wordplay.
'democrat' becomes 'd'.
'involved in' means one lot of letters goes inside another.
'victory' becomes 'win' (a win is a victory).
'before' says to put letters next to each other.
'autumn' becomes 'fall' (synonyms).
'win'+'fall'='winfall'
'd' inserted inside 'winfall' is 'WINDFALL'.
'for' is the link.
(Other definitions for windfall that I've seen before include "Stroke of luck" , "Lucky acquisition" , "Sudden and unexpected piece of good fortune" , "Unexpected gain" , "Piece of fortune - fruit on ground" .)