Improve aria until it becomes practical (11)
I believe the answer is:
utilitarian
'practical' is the definition.
(thesaurus)
'improve aria until it' is the wordplay.
'improve' indicates an anagram.
'aria'+'until'+'it'='ariauntilit'
'ariauntilit' anagrammed gives 'UTILITARIAN'.
'becomes' acts as a link.
(Other definitions for utilitarian that I've seen before include "Practical rather than attractive" , "Philosopher" .)