Steel drum keeping time with first of trumpeters in procession (7)
I believe the answer is:
pageant
'procession' is the definition.
(I've seen this before)
'steel drum keeping time with first of trumpeters' is the wordplay.
'steel drum' becomes 'pan' (steel pans).
'keeping' is an insertion indicator.
'time' becomes 'age' (an age is a period of time).
'with' is a charade indicator (letters next to each other).
'first of trumpeters' becomes 't' (1st letter of 'trumpeters').
'pan' going around 'age' is 'pagean'.
'pagean'+'t'='PAGEANT'
'in' is the link.
(Other definitions for pageant that I've seen before include "Rich parade" , "Spectacular ceremony" , "Splendid procession, parade" , "Spectacular parade" , "Parade with tableaux" .)