Farm building in Epping, converted (6)
I believe the answer is:
pigpen
'farm building' is the definition.
(enclosure for pigs)
'epping converted' is the wordplay.
'converted' indicates anagramming the letters.
'epping' with letters rearranged gives 'PIGPEN'.
'in' acts as a link.
(Other definitions for pigpen that I've seen before include "tip" , "that accommodates swine" , "Sty (American)" , "Sty for swine" .)