The most common and most likely answer to this crossword clue is the 6 letter word TURNED
I've seen this crossword clue in The Guardian
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More clues leading to the result TURNED
Buddy explains!
The straight part
We know that "suddenly felt sick" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case suddenly felt sick = turned.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does TURNED mean?
TURNED verb- (heading) to make a non-linear physical movement.
- (heading) To change condition or attitude.
- To change one's course of action; to take a new approach.
- (usually with over) To complete.
- To make (money); turn a profit.
- Of a player, to go past an opposition player with the ball in one's control.
- To undergo the process of turning on a lathe.
- To bring down the feet of a child in the womb, in order to facilitate delivery.
- To invert a type of the same thickness, as a temporary substitute for any sort which is exhausted.
- To translate.
- To magically or divinely attack undead.