Some fish supper with dear Parisian mistress? (13)
I believe the answer is:
schoolteacher
'mistress?' is the definition.
(schoolmistress)
'some fish supper with dear parisian' is the wordplay.
'some fish' becomes 'school' (school can mean a group of fish).
'supper' becomes 'tea'.
'with' means one lot of letters go next to another.
'dear parisian' becomes 'cher' ('dear' in French).
'school'+'tea'+'cher'='SCHOOLTEACHER'
(Other definitions for schoolteacher that I've seen before include "Educator" , "Instructor" , "Master, say" , "Chips perhaps" , "tutor" .)