Ready for collection (3)
I believe the answer is:
I believe this clue is a double definition.
'ready' is the first definition.
(similar in meaning)
'collection' is the second definition.
(set is a kind of collection)
'for' is the link.
(Other definitions for set that I've seen before include "Hardened" , "Ready" , "Series of tennis games" , "Group of items of the same kind" , "Group; unchanging" .)