Wistfully mournful (7)
I believe the answer is:
elegiac
'wistfully mournful' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for elegiac that I've seen before include "Wistful, mournful" , "Plaintive" , "Wistfully mournful" , "Mournful or sad as poem may be" , "Thoughtful" .)