Join into one

FUSE

Think of what happens when two metals are heated together to become a single piece, or when ideas blend seamlessly.

"Join into one" is a straightforward definition clue pointing to a word that means combining things into a single unit. The answer "FUSE" fits perfectly because it literally means to merge or blend together, like fusing metals or ideas. There’s no hidden wordplay here—it’s a direct match where the clue and answer share the same core meaning. Think of it like melting two pieces of metal into one solid piece.