Nervous tension (6)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
stress
'nervous tension' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for stress that I've seen before include "Draw attention to" , "Tension; emphasis" , "Cause of crack" , "Dwell on" , "Tension - accent" .)