Most unusual assignment for knights to receive is not for commoners (9)
I believe the answer is:
quaintest
'most unusual' is the definition.
(I've seen this before)
'to receive is not for commoners' is the wordplay.
'to receive' is an insertion indicator.
'is not' becomes 'ain't' ('ain't' is a non-standard form of 'isn't').
'for commoners' becomes 'quest' (I can't explain this - if you can you should give a lot more credence to this answer).
'aint' going within 'quest' is 'QUAINTEST'.
'assignment for knights' is the link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Another definition for quaintest that I've seen is " Most unusual".)
