My parse's wrong, assuming 2's first letter is M? (9)
I believe the answer is:
spymaster
'my parse's wrong assuming' is the definition.
I know nothing about this answer so I cannot tell whether this works.
'2's first letter is m?' is the wordplay.
I cannot quite see how this works, but
'2's' could be 's' and 's' is found in the answer.
'first' could be 'a' (first letter of the alphabet) and 'a' is found in the answer.
'letter' could be 'y' (Y is a letter of the alphabet) and 'y' is present in the answer.
'm?' could be 'm' and 'm' is located 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 spymaster that I've seen before include "head of 6?" , "Messy part (anag) - M?" , "007's boss?" , "Eg, head of MI6" , "Eg, Bond's M" .)