Register liable to change again (7)
I believe the answer is:
readapt
'change again' is the definition.
('adapt' is an answer for 'change' so perhaps 'readapt' is OK for 'change again')
'register liable' is the wordplay.
'register' becomes 'read' ('read' can be a synonym of 'register').
'liable' becomes 'apt' ('apt' can be a synonym of 'liable').
'read'+'apt'='READAPT'
'to' acts as a link.
(Other definitions for readapt that I've seen before include "Once again modify" , "again demonstrate versatility" , "undergo further change" , "Again adjust to changed conditions" , "make further modifications" .)