Highlight emotional tension (6)
I believe the answer is:
stress
I believe this clue is a double definition.
'highlight' is the first definition.
(I know that highlight is a more specific form of the action bring out)
'emotional tension' is the second definition.
(I've seen this before)
(Other definitions for stress that I've seen before include "Emotional tension" , "Tension, pressure" , "suffering" , "Cause of crack" , "Tension - accent" .)