With the Italian stress rule a syllable is equivalent to a vowel (and surrounding, but unexciting, consonants). I'm quite sure there is no accent there, dictionaries aside - it doesn't need one because the stress is where it's expected, on the second-last vowel. The use of accents is limited to situations where the stress is in an unexpected place, and even then, they aren't always used. Approximate pronunciation is "mah-cel-le-REE-ah"

Edit: Sorry, that should be "mah-chel-le-REE-ah". I missed the English "ch" because in Italian c followed by e automatically makes that sound.