Garden plant making autumn stir (10)
I believe the answer is:
nasturtium
'garden plant' is the definition.
'nasturtium' can be an answer for 'plant' (nasturtium is a kind of plant). I'm not certain of the 'garden' bit.
'making autumn stir' is the wordplay.
'making' indicates an anagram.
'autumn'+'stir'='autumnstir'
'autumnstir' anagrammed gives 'NASTURTIUM'.
Can you help me to learn more?
(Other definitions for nasturtium that I've seen before include "flowering plant" , "Common trailing plant" , "ITMA's U-turn (anag) - flower" , "bloomer" , "Garden climber" .)