Taking people such as ourselves in is really wrong (6,3)
I believe the answer is:
mortal sin
'wrong' is the definition.
(thesaurus)
'taking people such as ourselves in is really' is the wordplay.
I cannot really understand how this works, but
'people' could be 'mortals' ('mortal' can be a synonym of 'person') and 'mortals' is found within the answer.
'as' could be 'in' (I've seen this in other clues) and 'in' is found within the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for mortal sin that I've seen before include "heinous act" , "It causes the death of the soul - not venial" .)