Race round shrub (4)
I believe the answer is:
acer
'shrub' is the definition.
(I've seen this before)
'race round' is the wordplay.
'round' is an anagram indicator.
'race' with letters rearranged gives 'ACER'.
(Other definitions for acer that I've seen before include "Care about this tree" , "Tree or shrub of the maple genus" , "Care about the maple?" , "Tree of maple family" , "ornamental tree" .)