Solemn place of burial (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)
'place of burial' is the second definition.
(I've seen this before)
(Other definitions for grave that I've seen before include "Serious in a crypt" , "French accent; very serious" , "Solemn; tomb" , "Grievous, serious" , "of importance" .)