Kentish society's yellow climbing flowers (5)
I believe the answer is:
roses
'flowers' is the definition.
(rose is a type of flower)
'kentish society's yellow climbing' is the wordplay.
'kentish' becomes 'SE' (South East).
'society' becomes 's' (common abbreviation in names of organisations).
'yellow' becomes 'or' (heraldic term).
'climbing' shows that the letters should be reversed in order (in a down clue, letters climb up).
'se'+'s'+'or'='sesor'
'sesor' backwards is 'ROSES'.
(Other definitions for roses that I've seen before include "These flowers in one's cheeks usually denote health" , "Thorny plants" , "Flowers for watering cans?" , "''They are not long, the days of wine and ...'' (Dowson)" , "Blooms" .)