Angel fish enthrals cockney woman (6)
I believe the answer is:
cherub
'angel' is the definition.
(cherub is a kind of angel)
'fish enthrals cockney woman' is the wordplay.
'fish' becomes 'chub' (chub is a kind of fish**).
'enthrals' means one lot of letters goes inside another.
'cockney woman' becomes 'er' ('her' said with a cockney accent, dropping the 'H').
'chub' placed around 'er' is 'CHERUB'.
(Other definitions for cherub that I've seen before include "goody-goody?" , "overweight child" , "A heavenly baby" , "Sweet, innocent child" , "Innocent youngster" .)