Joshua's father's sister (3)
I believe the answer is:
nun
This clue is a double definition.
'joshua's father's' is the first definition.
(I've seen this before)
'sister' is the second definition.
(thesaurus)
(Other definitions for nun that I've seen before include "nuisance in pine forest" , "Sister of mercy" , "Fancy pigeon variety" , "Holy sister" , "Domestic fancy pigeon" .)