Excellent silver put around goddess (4)
I believe the answer is:
gaia
'goddess' is the definition.
(thesaurus)
'excellent silver put around' is the wordplay.
'excellent' becomes 'ai' (resembles 'A1', old-fashioned term for excellent).
'silver' becomes 'Ag' (Ag is the chemical symbol for silver).
'put around' says the letters should be written in reverse.
'ai'+'ag'='aiag'
'aiag' written backwards gives 'GAIA'.
(Other definitions for gaia that I've seen before include "The earth viewed as a large organism (Lovelock)" , "Greek goddess of the Earth" , "Earth personified" .)