Breeding ground teacher associated with Pistol’s world (6,3)
I believe the answer is:
oyster bed
'breeding ground' is the definition.
(where oysters breed)
'teacher associated with pistol's world' is the wordplay.
'teacher' becomes 'BEd' (Bachelor of Education).
'associated with' is a charade indicator (letters next to each other).
'pistol's world' becomes 'oyster' ('the world's mine oyster' - Shakespeare's Pistol).
'bed' put after 'oyster' is 'OYSTER-BED'.
(Other definitions for oyster bed that I've seen before include "Source of pearls" , "breeding ground" , "stew, perhaps" , "A source of seafood" , "seafood supplier" .)