Cockney’s rent causing outrage? (3)
I believe the answer is:
ire
I believe this clue is a double definition.
'cockney's rent' is the first definition.
('hire' - rent can mean to hire something out - said with a cockney accent, dropping the 'H')
'outrage?' is the second definition.
(outrage is a kind of ire)
'causing' is the link.
(Other definitions for ire that I've seen before include "Anger, rage" , "heat" , "Choler" , "'Anger, wrath (3)'" , "Strong emotion" .)