Mine changed in manner (4)
I believe the answer is:
mien
'manner' is the definition.
(mien can mean a manner or attitude)
'mine changed' is the wordplay.
'changed' indicates anagramming the letters.
'mine' with letters rearranged gives 'MIEN'.
'in' is the link.
(Other definitions for mien that I've seen before include "A face - maybe mine" , "Comportment" , "Dignified manner" , "The carriage" , "A person's demeanour" .)