Young female writer before detox essentially wasted (8)
I believe the answer is:
misspent
'wasted' is the definition.
(I've seen this before)
'young female writer before detox essentially' is the wordplay.
'young female' becomes 'miss' (I've seen this in another clue).
'writer' becomes 'pen' (something which writes).
'before' is a charade indicator (letters next to each other).
'essentially' indicates the central letters.
The middle letter of 'detox' is 't'.
'miss'+'pen'+'t'='MISSPENT'
(Other definitions for misspent that I've seen before include "Like many a youth" , "troublesome youth?" , "Squandered" , "Wasted (as youth)" , "wasted away?" .)