I guessed it was an anagram and there are only two options if the given letters are correct - YESK or YKES. The first one seemed to be more likely so I looked it up in Chambers Dictionary and there it was as YEX (alternative to YESK) meaning to hiccup, belch or spit. It is apparently Scottish dialect - I always think that crosswords would be easier if one had been brought up in Scotland!(which I wasn't)
You must ask Father Christmas to bring you a nice new Chambers Dictionary.