European wife mostly not returning (6)
I believe the answer is:
briton
'european' is the definition.
(I know that Briton is a type of european)
'wife mostly not returning' is the wordplay.
'wife mostly' becomes 'brit' (I can't justify this - if you can you should believe this answer much more).
'not' becomes 'no' (negative).
'returning' shows that the letters should be reversed in order.
'no' written backwards gives 'on'.
'brit'+'on'='BRITON'
Can you help me to learn more?
(Other definitions for briton that I've seen before include "Ancient inhabitant of southern UK" , "Native of Great Britain" , "Native of England, Wales or Scotland" , "Never a slave, says the song" , "UK citizen" .)