Superior Theresa, fantastic in role (7,5)
I believe the answer is:
streets ahead
'superior' is the definition.
I know nothing about this answer so I cannot judge whether this works.
'theresa fantastic in role' is the wordplay.
'fantastic' indicates an anagram (a fantastic or improbable ordering of the letters).
'in' indicates putting letters inside.
'role' becomes 'stead' (stead is a kind of role).
'theresa' with letters rearranged gives 'reetsah'.
'reetsah' going into 'stead' is 'STREETS AHEAD'.
Can you help me to learn more?
(Other definitions for streets ahead that I've seen before include "much better" , "vastly superior" , "right at the front" , "A long way in front" , "Greatly superior" .)