Solemn accent (5)
I believe the answer is:
grave
I believe this clue is a double definition.
'solemn' is the first definition.
(grave can mean solemn or serious)
'accent' is the second definition.
(I know that grave is a type of accent)
(Other definitions for grave that I've seen before include "Stern, serious" , "Solemn; tomb" , "Dignified" , "Serious in cemetery?" , "In which to lay a corpse" .)