Goes back in to find tenants who have ingested drug (8)

'goes back in to' is the definition.
I know nothing about this answer so I cannot judge whether it can be defined by this definition.

'tenants who have ingested drug' is the wordplay.
I cannot really understand how this works, but
'drug' could be 'e' (E is another name for ecstasy) and 'e' is located in the answer.
'tenants' could be 'renters' ('renter' can be a synonym of 'tenant') and 'renters' is found within the remaining letters.
No letters remain.
This may be the basis of the clue (or it may be nonsense).

'find' is the link.

Can you help me to learn more?