Girl writer, given time, squandered (8)
I believe the answer is:
misspent
'squandered' is the definition.
(thesaurus)
'girl writer given time' is the wordplay.
'girl' becomes 'miss' (I've seen this before**).
'writer' becomes 'pen' (I've seen this before).
'given' is a charade indicator (letters next to each other).
'time' becomes 't'.
'miss'+'pen'+'t'='MISSPENT'
(Other definitions for misspent that I've seen before include "Dissipated" , "youth? Sort of" , "wasted away?" , "Passed the time unwisely, as a youth perhaps" , "Squandered" .)