Bluffer's declaration

IRAISE

Think of what a poker player might say when they’re betting big without the cards to back it up.

This clue plays on the phrase "raise you" in poker, where a bluffer might declare they're increasing the bet. Split "I raise" into "I" and "raise," then read it as a single word to get "IRAISE." The surface meaning hints at a boastful claim, while the wordplay turns a poker move into the answer.