Circulation of air, tireless, not requiring a purifier? (10)
I believe the answer is:
steriliser
'purifier?' is the definition.
'circulation of air tireless not requiring a' is the wordplay.
'circulation of' indicates an anagram (letters circulated around).
'not requiring' indicates named letters should be taken away.
'air'+'tireless'='airtireless'
'airtireless' with 'a' taken away is 'irtireless'.
'irtireless' with letters rearranged gives 'STERILISER'.
(Other definitions for steriliser that I've seen before include "Bacteria-destroyer" , "one should keep things clean" .)