Garden Richard's built around ornament (6)
I believe the answer is:
enrich
'ornament' is the definition.
(thesaurus)
'garden richard's built around' is the wordplay.
'around' indicates a hidden word.
'ENRICH' is hidden within 'garden richards built'.
(Other definitions for enrich that I've seen before include "Concentrate" , "Make wealthy or improve the quality" , "Improve the quality by adding things" , "Add to and improve" , "Add nutrients to" .)