Acquaintance needing change of air housed by relatives accepting it (11)
I believe the answer is:
familiarity
'acquaintance' is the definition.
(synonyms)
'change of air housed by relatives accepting it' is the wordplay.
'change of' indicates an anagram.
'housed by' is an insertion indicator.
'relatives' becomes 'family' (I can't explain this - if you can you should give a lot more credence to this answer).
'accepting' is an insertion indicator.
'air' anagrammed gives 'ari'.
'family' enclosing 'it' is 'famility'.
'ari' going within 'famility' is 'FAMILIARITY'.
'needing' is the link.
Can you help me to learn more?
(Other definitions for familiarity that I've seen before include "that produces contempt" , "Intimacy" , "Breeds contempt" .)