Split monthly expense, perhaps (4)
I believe the answer is:
rent
'split' is the definition.
(past tense of 'rend' meaning to split)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for rent that I've seen before include "Let out - torn" , "slashed" , "Tear; lease" , "Tenant's fee" , "Payment - in pieces" .)