Ornate legendary bird circles round about (6)
I believe the answer is:
rococo
'ornate' is the definition.
(thesaurus)
'legendary bird circles round about' is the wordplay.
'legendary bird' becomes 'roc' (I've seen this before).
'circles' becomes 'oo' (resembles two O's).
'round' is an insertion indicator.
'about' becomes 'c' (abbreviation for 'circa'**).
'oo' enclosing 'c' is 'oco'.
'roc'+'oco'='ROCOCO'
(Other definitions for rococo that I've seen before include "Ornate late baroque style" , "Florid style" , "Eighteenth-century French architectural style" , "Style of architecture, art, etc associated with the time of Louis XV" , "Grotesque" .)