Solemn pronouncement (4)
I believe the answer is:
oath
'solemn pronouncement' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for oath that I've seen before include "A solemn undertaking to tell the truth" , "It's taken in court" , "A curse - or a pledge" , "Solemn promise to tell the truth or be loyal" , "blasphemy" .)