Each year, group of bigwigs hosts a ceremony (9)
I believe the answer is:
pageantry
'ceremony' is the definition.
(I know that pageantry is a type of ceremony)
'each year group of bigwigs hosts a' is the wordplay.
'each year' becomes 'PA' (abbreviation for per annum).
'group of bigwigs' becomes 'gentry' (genteel people).
'hosts' indicates putting letters inside (inserted letters are welcomed or hosted).
'gentry' placed around 'a' is 'geantry'.
'pa'+'geantry'='PAGEANTRY'
(Other definitions for pageantry that I've seen before include "Splendid display" , "Show" , "Spectacle" .)