Voice changes a lot (4)
I believe the answer is:
alto
'voice' is the definition.
(alto is a kind of voice)
'changes a lot' is the wordplay.
'changes' indicates an anagram.
'a'+'lot'='alot'
'alot' anagrammed gives 'ALTO'.
(Other definitions for alto that I've seen before include "Woman's singing voice" , "Counter-tenor or contralto" , "Key old > male who scores high" , "Singing voice between tenor and soprano" , "Voice part" .)