Stops holding up the flowers! (5)
I believe the answer is:
stems
'stops' is the definition.
(stemming is a kind of stopping)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for stems that I've seen before include "Structures that support plants" , "Stops" , "things growing?" , "Dams" , "gets arrested?" .)