It = Subject AND 's every bit as tough as they say = Predicate consisting of:
- 's = Verb
- every bit as tough as they say = Predicative Complement
Every bit is an idiom which means
quite; just; equally (used in comparisons with as)
- every bit as funny as the other show (Collins)
In your sentence, every bit is a Noun Phrase, being part of the Predicative Complement ("every bit as tough as they say"). The NP every bit is functioning as a modifier of the adjective "tough", answering to the question "how tough?". Within this NP, every is an adjective which functions as a determinative of the noun bit.
As the phrase does not contain any adverb, it cannot be an adverb phrase, although:
- it carries a meaning which could be expressed by an adverb
- it modifies an adjective in the way an adverb could modify it.
It can, however, be replaced by an adverb:
It's equally/comparably as tough as they say unless you're genius like Meeks.
Note that every bit is informal. (Free Dictionary)