One of three in a mix? (7)
I believe the answer is:
numeral
'mix?' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.
'one of three in a' is the wordplay.
I cannot quite understand how this works, but
'one' could be 'me' (a setter might use 'one' to humourously mean 'me') and 'me' is present in the answer.
'a' is found in the answer.
The remaining letters 'nurl' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for numeral that I've seen before include "Symbol for number" , "See 22" , "Figure denoting a number" , "Rule man (anag) - digit" , "Eg, two or seven" .)