Heavily decorated knight entering to make a speech (6)
I believe the answer is:
ornate
'heavily decorated' is the definition.
(I've seen this before)
'knight entering to make a speech' is the wordplay.
'knight' becomes 'n' (chess).
'entering' means one lot of letters goes inside another.
'to make a speech' becomes 'orate' (I've seen this before).
'n' going inside 'orate' is 'ORNATE'.
(Other definitions for ornate that I've seen before include "(Of literary style) complex and with unusual words" , "Heavily decorated" , "Highly decorated" , "Detailed" , "Rich in decorative detail" .)