Female flier starting at six beat Rita before ten (8)
I believe the answer is:
aviatrix
'female flier' is the definition.
(I've seen this before)
'starting at six beat rita before ten' is the wordplay.
'starting' indicates taking the first letters.
'six' becomes 'VI' (roman numeral).
'beat' indicates anagramming the letters.
'before' means one lot of letters go next to another.
'ten' becomes 'x' (roman numeral).
The first letter of 'at' is 'a'.
'rita' anagrammed gives 'atri'.
'a'+'vi'+'atri'+'x'='AVIATRIX'
(Other definitions for aviatrix that I've seen before include "Pioneer travelling" , "Female flier" , "eg Amy Johnson" , "A female pilot in early days of flying" , "She flies" .)