Intensely distressing (6)
I believe the answer is:
tragic
'intensely distressing' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for tragic that I've seen before include "'Very, very sad (6)'" , "Disastrous, desperately sad" , "Unfortunate" , "Heart-rending" , "Resulting in great loss" .)