Firm prepared collection (3)
I believe the answer is:
set
This clue is a triple definition!
'firm' is the first definition.
(both can mean fixed)
'prepared' is the second definition.
(set up or ready)
'collection' is the third definition.
(set is a kind of collection)
(Other definitions for set that I've seen before include "Congeal" , "Hard; place" , "Class" , "become firm" , "Mount (precious stone)" .)