Repaired noisier air-freshener (7)
I believe the answer is:
ioniser
'air-freshener' is the definition.
I can't tell whether this definition defines the answer.
'repaired noisier' is the wordplay.
'repaired' indicates an anagram.
'noisier' anagrammed gives 'IONISER'.
Can you help me to learn more?
(Other definitions for ioniser that I've seen before include "Producer of charged particles to freshen air" , "pollution remover" , "something to freshen air" , "maybe this would improve air quality?" , "Device improving room air quality" .)