Grand, possibly regal (5)
I believe the answer is:
large
'grand' is the definition.
(thesaurus)
'possibly regal' is the wordplay.
'possibly' indicates anagramming the letters.
'regal' with letters rearranged gives 'LARGE'.
(Other definitions for large that I've seen before include "Big < burly" , "Gross" , "Big, outsize" , "Titanic" , "Extensive" .)