Mournful in tone (7)
I believe the answer is:
elegiac
'mournful in tone' is the definition.
(as in an elegy)
This is all the clue.
(Other definitions for elegiac that I've seen before include "Expressing poetic sorrow for something past" , "Mournful as in Gray's poem" , "Wistful, mournful" , "Lie in cage being poetically mournful" , "Thoughtful" .)