While reading a book, I came across this sentence:
[...], finishing with a slither of lemon tart or apple cake.
Looking up the word slither I didn't get any satisfying results.
On OALD I found the definition of "to slither" which means to move forwards either in a smooth way (to slide) or uncontrolled (to glide).
In the given sentence this would only make sense if it's about how smooth this lemon tart goes down the gullet. But I don't think that it is meant like this. Moreover, wouldn't it be "a slithering lemon tart"?!
Thinking about the sentence and what it could be I'm assuming that it could mean "a part of", but I don't find any proof.
So, which is the correct meaning of "a slither of" and which words are best synonyms for it?