Windfall (7)
'windfall' is the definition.
(situation leading to an increase in wealth)
This is all the clue.
(Other definitions for bonanza that I've seen before include "Sudden influx of wealth" , "Lucky strike of wealth" , "A striking example" , "Source of great and sudden wealth" , "Source of sudden wealth, windfall (7)" .)
'windfall' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for boon that I've seen before include "Gracious gift" , "Godsend" , "Blessing - sort of companion?" , "Favour, request" , "Something beneficial - a blessing" .)