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' anagrammed 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" .)