Room in church with fossil resin (7)
I believe the answer is:
chamber
'room' is the definition.
(I know that chamber is a type of room)
'church with fossil resin' is the wordplay.
'church' becomes 'ch' (abbreviation on maps etc).
'with' means one lot of letters go next to another.
'fossil resin' becomes 'amber' (I've seen this before).
'ch'+'amber'='CHAMBER'
'in' acts as a link.
(Other definitions for chamber that I've seen before include "posh room" , "A house of parliament" , "Bedroom" , "Room where a judge transacts business" , "Official room" .)