Nauseous and sweaty at first? Ugh! (4)
I believe the answer is:
sick
'nauseous' is the definition.
(I know that nauseous can be written as sick)
'sweaty at first? ugh' is the wordplay.
'at first?' suggests taking the first letters (I've seen 'at first' mean this).
'ugh' becomes 'ick' (I am not sure about this - if you are sure you should believe this answer much more).
The first letter of 'sweaty' is 's'.
's'+'ick'='SICK'
'and' acts as a link.
Can you help me to learn more?
(Other definitions for sick that I've seen before include "well? Hardly" , "not good" , "Bad" , "Ill, unwell" , "Ill; perverted" .)