Died clutching it, most unhappy, you make clear (6)
I believe the answer is:
stress
'make clear' is the definition.
The answer and definition can be both acts as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for stress that I've seen before include "Dwell on" , "what causes tension" , "result of being overworked" , "Ictus" , "Physical or mental over-exertion" .)