Arbitrary number checked by sharp staff includes one small digit (6)
I believe the answer is:
pinkie
'small digit' is the definition.
(I've seen this in another clue)
'arbitrary number checked by sharp staff includes one' is the wordplay.
I cannot really understand how this works, but
'number' could be 'pin' (I've seen this before) and 'pin' is found within the answer.
'one' could be 'i' (Roman numeral) and 'i' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for pinkie that I've seen before include "Smallest digit" , "An American little finger" , "The little finger in America" .)