Excellent silver brought back for goddess (4)
I believe the answer is:
gaia
'goddess' is the definition.
(thesaurus)
'excellent silver brought back' is the wordplay.
'excellent' becomes 'ai'.
'silver' becomes 'ag' (Ag is the chemical symbol for silver).
'brought back' shows that the letters should be reversed in order.
'ai'+'ag'='aiag'
'aiag' backwards is 'GAIA'.
'for' acts as a link.
(Other definitions for gaia that I've seen before include "Greek goddess of the Earth" , "Earth personified" , "The earth viewed as a large organism (Lovelock)" .)