Climate affected small climbing plant (8)
I believe the answer is:
clematis
'climbing plant' is the definition.
(I've seen this before)
'climate affected small' is the wordplay.
'affected' indicates anagramming the letters.
'small' becomes 's' (abbreviation - e.g. clothes size).
'climate' anagrammed gives 'clemati'.
'clemati'+'s'='CLEMATIS'
(Other definitions for clematis that I've seen before include "bloomer" , "Climbing garden plant" , "Garden climber" , "Ornamental climbing plant" , "Climbing plant with colourful flowers" .)