Musician, chaste? Around about 50/50 (7)
I believe the answer is:
purcell
'musician' is the definition.
(Henry Purcell 1659-1696)
'chaste? around about 5050' is the wordplay.
'chaste?' becomes 'pure' ('pure' can be similar in meaning to 'chaste').
'around' means one lot of letters goes inside another.
'about' becomes 'c' (circa abbreviation).
'5050' becomes 'LL' (two Ls, Roman numerals for 50).
'pure' going around 'c' is 'purce'.
'purce'+'ll'='PURCELL'
(Other definitions for purcell that I've seen before include "Composer of Dido and Aeneas, d. 1695" , "Henry -, C 17 composer" , "English composer (Dido and Aeneas)" , "organist" , "Henry --, English baroque composer" .)