Wasted time supporting unmarried female writer (8)
I believe the answer is:
misspent
'wasted' is the definition.
(I've seen this before)
'time supporting unmarried female writer' is the wordplay.
'time' becomes 't'.
'supporting' says to put letters next to each other (in a down clue, some letters go below others).
'unmarried female' becomes 'miss'.
'writer' becomes 'pen' (I've seen this before).
'miss'+'pen'='misspen'
't' put after 'misspen' is 'MISSPENT'.
(Other definitions for misspent that I've seen before include "having used money unwisely" , "Squandered" , "youth? Sort of" , "Passed the time unwisely, as a youth perhaps" , "troublesome youth?" .)