Clematis endlessly battered in weather (7)
I believe the answer is:
climate
'weather' is the definition.
(I've seen this before)
'clematis endlessly battered' is the wordplay.
'endlessly' means to remove the last letter.
'battered' indicates anagramming the letters.
'clematis' with its final letter removed is 'clemati'.
'clemati' is an anagram of 'CLIMATE'.
'in' acts as a link.
(Other definitions for climate that I've seen before include "Prevailing public attitude" , "Came lit (anag.)" , "Mail, etc (anag.)" , "General weather conditions in an area" , "Prevailing state" .)