Decorated or terribly neat (6)
I believe the answer is:
ornate
'decorated' is the definition.
(I've seen this before)
'or terribly neat' is the wordplay.
'terribly' is an anagram indicator.
'neat' with letters rearranged gives 'nate'.
'or'+'nate'='ORNATE'
(Other definitions for ornate that I've seen before include "Detailed" , "Over-decorated" , "Elaborately decorated, perhaps overdone" , "Fancy" , "(Of literary style) complex and with unusual words" .)