What get-out clause may do regarding rental agreement (7)
I believe the answer is:
release
'what get-out clause may do' is the definition.
(a get-out clause releases someone from a contract)
'regarding rental agreement' is the wordplay.
'regarding' becomes 're'.
'rental agreement' becomes 'lease' (I've seen this before).
're'+'lease'='RELEASE'
(Other definitions for release that I've seen before include "Let go" , "Authorise publication" , "New film" , "put out" , "loose" .)