Worry, being mixed race (4)
I believe the answer is:
care
'worry' is the definition.
(I've seen this before)
'mixed race' is the wordplay.
'mixed' is an anagram indicator.
'race' with letters rearranged gives 'CARE'.
'being' is the link.
(Other definitions for care that I've seen before include "Mind" , "Feel concern or interest" , "Be concerned or nurse" , "Race (anag.)" , "Have affection (for)" .)