Torn apart (4)
I believe the answer is:
'torn apart' is the definition.
(past tense of 'rend', to tear or rip)
This is all the clue.
(Other definitions for rent that I've seen before include "Landlord's due - that's torn it" , "money demanded by letter" , "Payment due to landlord" , "Payment by a tenant" , "opening" .)