"The farmer cooks in the priest's church."
Translation:Bonden lager mat i prestens kirke.
The definite suffix isn't used when the noun follows the possessive like this, as the possessive already clarifies that the noun is a definite/specific one. Just like in English you don't say "my the church".
In other possessive structures it will, however, be used:
"Bonden lager mat i kirken til presten."
"The farmer cooks food in the church of the priest."