Bullet for flowerbed visitor! (4)
I believe the answer is:
slug
'bullet' is the definition.
(I know that bullet can be written as slug)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for slug that I've seen before include "Bullet -- shot of liquor" , "slimy type" , "Heavy blow for snail lacking shell" , "Shell-less mollusc ? bullet" , "Live" .)