Ostentatious ceremony (4)
I believe the answer is:
pomp
'ostentatious ceremony' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for pomp that I've seen before include "Stately and splendid display" , "Ostentatious ceremony" , "Great ceremony" , "Ceremony and splendour" , "Solemn ceremony and splendid display" .)