It's pronounced:
/s@k@:/
with stress on the SECOND syllable. (see
SAMPA for meaning of symbols). Actually, I don't really know how to write the correct pronunciation of the second syllable - it's one of those French things where the "r" is almost, but not quite pronounced. (The origin of the word is French).
It does not rhyme with "sucker". At least, it's not supposed to.
Rommie