Goes back in to make second deduction, which is welcomed by tenants (8)

'goes back in to make second deduction' is the definition.
I don't know anything about this answer so I can't tell whether this works.

'which is welcomed by tenants' is the wordplay.
'which' becomes 'e' (I can't explain this - if you can you should give a lot more credence to this answer).
'is welcomed by' indicates putting letters inside (inserted letters are welcomed in).
'tenants' becomes 'renters' ('renter' can be a synonym of 'tenant').
'e' inserted into 'renters' is 'REENTERS'.

Can you help me to learn more?