I’ve become a fan of Richard Nordquist’s Grammar & Composition pages at about.com.
Here is Dr. Nordquist’s definition of clause:
A group of words that contains a subject and a predicate. A clause may be either a sentence (independent clause) or a sentence-like construction included within another sentence (dependent clause).
“Don’t ever argue with the big dog, [INDEPENDENT CLAUSE] because the big dog is always right [DEPENDENT CLAUSE] .
Deputy Marshal Samuel Gerard in The Fugitive, 1993