Care about tree (4)
I believe the answer is:
acer
'tree' is the definition.
(acer is a type of tree)
'care about' is the wordplay.
'about' indicates anagramming the letters.
'care' with letters rearranged gives 'ACER'.
(Other definitions for acer that I've seen before include "Care about the maple?" , "Tree with winged fruit" , "Care about this tree" , "ornamental tree" , "Plant" .)