Decorated knight coming in to make a speech (6)
I believe the answer is:
ornate
'decorated' is the definition.
(I've seen this before)
'knight coming in to make a speech' is the wordplay.
'knight' becomes 'n' (chess).
'coming in to' is an insertion indicator.
'make a speech' becomes 'orate' (I've seen this before).
'n' put within 'orate' is 'ORNATE'.
(Other definitions for ornate that I've seen before include "Over-decorated" , "Rococo" , "Elaborately decorated, perhaps overdone" , "Lavishly decorated" , "Excessively decorated" .)