Tom introducing European goddess (6)
I believe the answer is:
hecate
'goddess' is the definition.
(I've seen this before)
'tom introducing european' is the wordplay.
'tom' becomes 'he-cat' (tom can mean a male cat).
'introducing' says to take the initial letters.
The first letter of 'european' is 'e'.
'hecat'+'e'='HECATE'
(Other definitions for hecate that I've seen before include "Greek goddess associated with witchcraft and the ghost world" , "Greek goddess of witchcraft and ghosts" , "Divine witch" , "underworld figure" , "Greek goddess of the Underworld" .)