Clare, unfortunately, is plain (5)
I believe the answer is:
clear
'is plain' is the definition.
('clear' can be a synonym of 'plain')
'clare unfortunately' is the wordplay.
'unfortunately' is an anagram indicator.
'clare' with letters rearranged gives 'CLEAR'.
(Other definitions for clear that I've seen before include "Not obstructed" , "Distinct - obvious" , "Obvious; remove obstructions from" , "School near Windsor" , "Open; not cloudy" .)