How quickly the head said "No, no"? (2,3,6)
I believe the answer is:
in two shakes
'how quickly the head' is the definition.
I don't know anything about this answer so I can't tell whether it can be defined by this definition.
'said no no?' is the wordplay.
I cannot really understand how this works, but
'said' could be 't' (I've seen this in other clues) and 't' is found in the answer.
'no' could be 'o' (O resembles 0) and 'o' is present in the answer.
'no?' could be 'n' (common abbreviation) and 'n' 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?
(Another definition for in two shakes that I've seen is " Quickly".)