At home, use other cohabiter (9)
I believe the answer is:
housemate
'cohabiter' is the definition.
'at home use other' is the wordplay.
'other' is an anagram indicator.
'at'+'home'+'use'='athomeuse'
'athomeuse' with letters rearranged gives 'HOUSEMATE'.
(Other definitions for housemate that I've seen before include "One sharing accommodation" , "person to live with" , "Co-tenant" , "One who shares a residence" .)