Composer making six valid changes (7)
I believe the answer is:
vivaldi
'composer' is the definition.
(composer Antonio Vivaldi)
'six valid changes' is the wordplay.
'six' becomes 'VI' (Roman numerals).
'changes' is an anagram indicator.
'valid' anagrammed gives 'valdi'.
'vi'+'valdi'='VIVALDI'
'making' acts as a link.
(Other definitions for vivaldi that I've seen before include "Italian composer of 'The Four Seasons'" , "Baroque Venetian composer, d.1741" , "Italian composer known as "the red priest"" , "Italian composer (the Red Priest) , d.1741" , "Venetian composer ("The Red Priest"), d. 1741" .)