Fresh, clean air, without a trace of smell or of some poisonous element (9)
I believe the answer is:
arsenical
'or of some poisonous element' is the definition.
I can't tell whether this definition defines the answer.
'fresh clean air without a trace of smell' is the wordplay.
'fresh' indicates an anagram.
'without' indicates putting letters inside ('without' can be similar in meaning to 'outside').
'a trace of' indicates taking the first letters.
The first letter of 'smell' is 's'.
'clean'+'air'='cleanair'
'cleanair' with letters rearranged gives 'arenical'.
'arenical' enclosing 's' is 'ARSENICAL'.
Can you help me to learn more?
(Other definitions for arsenical that I've seen before include "Mortal" , "containing poison" , "deadly combination" , "Like a certain element" .)