Truthful, female over material (7)
I believe the answer is:
factual
'truthful' is the definition.
(thesaurus)
'female over material' is the wordplay.
'female' becomes 'f' (common abbreviation).
'over' says to put letters next to each other (in a down clue, some letters go over others).
'material' becomes 'actual' (both can mean real).
'f'+'actual'='FACTUAL'
(Other definitions for factual that I've seen before include "Related to the truth" , "Based on real events" , "Based on things known to be true" , "True-to-life" , "Based on reality" .)