A most unusual arrow poison (6)
I believe the answer is:
curare
'arrow poison' is the definition.
(I've seen this before)
'a most unusual' is the wordplay.
'a most' becomes 'cu' (I can't justify this - if you can you should give a lot more credence to this answer).
'unusual' becomes 'rare' (rare can mean unusual or odd).
'cu'+'rare'='CURARE'
Can you help me to learn more?
(Other definitions for curare that I've seen before include "Poison used on darts" , "Paralysing plant poison" , "Poison put on arrows" , "Arrow poison" , "Poison applied to darts" .)
