I keep thinking this one is plural. /0\
Níor chuala mé an focal seo riamh!
how is this word pronounced?
You can hear the unlenited form here
Along with galaxy's link, the lenited form has a sound once described to me as "...somewhere between SH and a cat hissing, it is IPA /ç/." at the beginning. If you speak German it is the "Ichlaut" as heard in "ich" and "bücher"
Depending on where you're from, the same sound can also be heard in some English words such as the "h" in "human" and "hue." :)
Why is employer wrong?
Because your boss isn't necessarily your employer, and ceannasaí isn't the Irish for "employer" (fostóir).