Female succeeding yours truly in superior grade (8)
I believe the answer is:
classify
'grade' is the definition.
(I've seen this before)
'female succeeding yours truly in superior' is the wordplay.
'female' becomes 'f' (common abbreviation).
'succeeding' means one lot of letters go next to another (succeeding can mean going after or following).
'yours truly' becomes 'I' (the person who set this crossword).
'in' is an insertion indicator.
'superior' becomes 'classy' (classy can mean superior or elite).
'f' after 'i' is 'if'.
'if' placed within 'classy' is 'CLASSIFY'.
(Other definitions for classify that I've seen before include "Arrange systematically by group (8)" , "Sort by category" , "Arrange in categories" , "Arrange in divisions" , "catalogue?" .)