So you know it will nauseate you (6)
I believe the answer is:
sicken
'nauseate you' is the definition.
'sicken' can be an answer for 'nauseate' (synonyms). I am unsure of the 'you' bit.
'so you know it will' is the wordplay.
I cannot really see how this works, but
'so' could be 'sic' ('so' in Latin) and 'sic' is present in the answer.
'know' could be 'ken' (I've seen this in another clue) and 'ken' is located in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for sicken that I've seen before include "Make ill or nauseate" , "Become ill" , "Become unwell" , "Make ill or totally disgust" .)