Death, figuratively, is serious (5)
I believe the answer is:
grave
This clue might be a double definition.
'death' is the first definition.
(grave is a kind of death)
'is serious' is the second definition.
(both can mean solemn)
'figuratively' is the link.
This may not be correct. It may belong to one of the definitions.
Can you help me to learn more?
(Other definitions for grave that I've seen before include "Serious in a crypt" , "Solemn, serious" , "In which to lay a corpse" , "Dignified" , "Grim-faced" .)