Underground toiler opposing a goddess (7)
I believe the answer is:
minerva
'goddess' is the definition.
(thesaurus)
'underground toiler opposing a' is the wordplay.
'underground toiler' becomes 'miner'.
'opposing' becomes 'v' (abbreviation for versus).
'miner'+'v'+'a'='MINERVA'
(Other definitions for minerva that I've seen before include "deity of wisdom" , "Roman goddess of crafts and wisdom - a vermin (anag)" , "Roman goddess of learning" , "Divine female" , "female of great wisdom" .)