Concludes fern is damaged (6)
I believe the answer is:
infers
'concludes' is the definition.
(inferring is a kind of concluding)
'fern is damaged' is the wordplay.
'damaged' indicates anagramming the letters.
'fern'+'is'='fernis'
'fernis' with letters rearranged gives 'INFERS'.
(Other definitions for infers that I've seen before include "Concludes from the facts" , "Deduces, concludes" , "Deduces, gathers" , "'Derives, concludes (6)'" , "Takes or draws meaning from" .)