Game in which castle, perhaps, should be moved (4,3,6)
I believe the answer is:
pass the parcel
Here is my best explanation:
'game in' is the definition.
I don't know anything about this answer so I cannot judge whether this works.
'castle perhaps should be moved' is the subsidiary indication.
'castle perhaps' anagrams to 'pass the parcel'.
However, I am not sure how the anagram is indicated.
'which' is the link.
(Other definitions for pass the parcel that I've seen before include "Children's party game" and "Party game".)