This one was suggested by Matthew, Mr Libro. I’ve got to the point where I can’t remember whether I’ve covered a particular confusing word pair or not (see the link at the bottom of this post for the index to them all) but it is indeed a new one …
Slight is an adjective meaning not very sturdy or strong, or inconsiderable, small: “The rider was so slight that they feared he could not control the larger horse”; “There is a slight problem with your use of their and there, have a look at Liz’s Troublesome Pairs posts”. A slight (noun) is a kind of insult which is based around not showing someone the appropriate level of respect or attention: “He never bothered to read her blog posts, and she felt this slight keenly”.
Sleight is only actually ever found as part of the phrase ‘sleight of hand‘. This means manual dexterity, usually in the context of someone doing magic/conjuring tricks. By extension, it has also come to mean skilful deception of any kind, as more of a metaphor.
“He gained a slight advantage by employing sleight of hand and misleading the other runners as to the direction to take. However, as it was only a slight advantage, they soon caught up and beat him”.