Dad’s not French! (3)
I believe the answer is:
pas
'dad's not french' is the definition.
I can't judge whether this definition defines the answer.
'dad's not french' is the wordplay.
'dad' becomes 'pa' ('pa' can be a synonym of 'dad').
'not french' becomes 's' (I can't explain this - if you can you should give a lot more credence to this answer).
'pa'+'s'='PAS'
Can you help me to learn more?
(Other definitions for pas that I've seen before include "A bit of ballet" , "Dancing step" , "Dance movement" , "Ballet duet" , "Dance step" .)