Female, let down, prospered (8)
I believe the answer is:
flowered
'prospered' is the definition.
(flower can mean to prosper or do well)
'female let down' is the wordplay.
'female' becomes 'f' (abbreviation).
'let down' becomes 'lowered' (I've seen this in another clue).
'f'+'lowered'='FLOWERED'
(Other definitions for flowered that I've seen before include "Put forth blossom" , "Bloomed" , "opened out" , "Blossomed" , "Reached a peak" .)