Song verse transposed into A minor's source of educational material? (9)
I believe the answer is:
governess
'a minor's source of educational material?' is the definition.
(someone educating a minor)
'song verse transposed' is the wordplay.
'transposed' indicates an anagram.
'song'+'verse'='songverse'
'songverse' with letters rearranged gives 'GOVERNESS'.
'into' acts as a link.
(Other definitions for governess that I've seen before include "Supernanny?" , "Duenna" , "Mary Poppins, perhaps" , "Teacher" , "Becky Sharp, say" .)