Highlight anxiety (6)
I believe the answer is:
stress
I believe this clue is a double definition.
'highlight' is the first definition.
(I've seen this in another clue)
'anxiety' is the second definition.
(I've seen this before)
(Other definitions for stress that I've seen before include "Strain or accentuate" , "Tension; emphasis" , "Emphasize" , "Ictus" , "'Worry, pressure (6)'" .)