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' is the definition.
(I've seen this before)
'which castle perhaps should be moved' is the wordplay.
'castle perhaps' anagrams to 'PASS THE PARCEL'.
But, I am unsure how this is indicated.
'in' acts as a link.
(Other definitions for pass the parcel that I've seen before include "Children's party game", "Party game" and "Game".)