Passage of a good king, dressed with flourish (9)
I believe the answer is:
paragraph
'passage' is the definition.
(I've seen this before)
'a good king dressed with flourish' is the wordplay.
'good' becomes 'g' (abbreviation).
'king' becomes 'r' (r is abbreviation for rex).
'dressed with' indicates putting letters inside (inserted letters are dressed in other letters).
'flourish' becomes 'paraph' (flourish added to a signature).
'a'+'g'+'r'='agr'
'agr' going inside 'paraph' is 'PARAGRAPH'.
'of' is the link.
(Other definitions for paragraph that I've seen before include "Section of writing" , "short item" , "Unit of text" , "Section of written work" , "A group of connected sentences" .)