One put in homeless person’s file (7)
I believe the answer is:
dossier
'file' is the definition.
(both can mean a collection of information)
'one put in homeless person's' is the wordplay.
'one' becomes 'i' (Roman numeral).
'put in' is an insertion indicator.
'homeless person' becomes 'dosser' (I've seen this before).
'i' put inside 'dosser' is 'DOSSIER'.
(Other definitions for dossier that I've seen before include "File on a person or topic" , "Collection of documents on a subject" , "Papers containing detailed information about someone" , "Set of documents about person" , "Collection of documents on a topic" .)