Ain't it a change to be fairy queen! (7)
I believe the answer is:
titania
'be fairy queen' is the definition.
(I've seen this in another clue)
'ain't it a change' is the wordplay.
'change' is an anagram indicator.
'aint'+'it'+'a'='aintita'
'aintita' with letters rearranged gives 'TITANIA'.
'to' acts as a link.
(Other definitions for titania that I've seen before include "Oberon's better half?" , "Fairy queen (AMND)" , "Shakespeare's queen of the fairies" , "Fairy Queen (MND)" , "Bottom fan" .)