Knight for one rook and plan sacrificing a queen (5)
I believe the answer is:
rider
'knight' is the definition.
(I've seen this before)
'sacrificing a queen' is the wordplay.
'sacrificing' becomes 'ride' (I can't explain this - if you can you should give a lot more credence to this answer).
'a queen' becomes 'r' (r is abbreviation regina. e.g. in ER ).
'ride'+'r'='RIDER'
'for one rook and plan' is the link.
This may not be right. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for rider that I've seen before include "Legal document's additional clause" , "qualification" , "Added proviso" , "Jury's recommendation" , "Condition added to a legislative bill" .)