Unfortunately annual rut is affected (9)
I believe the answer is:
unnatural
'is affected' is the definition.
(both can mean false or inauthentic)
'unfortunately annual rut' is the wordplay.
'unfortunately' indicates an anagram (a bad or unfortunate spelling).
'annual'+'rut'='annualrut'
'annualrut' with letters rearranged gives 'UNNATURAL'.
(Other definitions for unnatural that I've seen before include "Lacking normal feelings of, say, affection" , "Affected" , "Abnormal; not spontaneous" , "Forced" , "Strange" .)