Air hampers toe treatment (10)
I believe the answer is:
atmosphere
'air' is the definition.
(I know that air can be written as atmosphere)
'hampers toe treatment' is the wordplay.
'treatment' is an anagram indicator (the letters must be processed or treated).
'hampers'+'toe'='hamperstoe'
'hamperstoe' anagrammed gives 'ATMOSPHERE'.
(Other definitions for atmosphere that I've seen before include "Air" , "Spirit" , "blue?" , "prevailing mood" , "character" .)