What's That Flat?

Heart transplant

In a heart transplant, a letter or series of letters is taken from inside one word and transplanted to another. Example: ONE clear, TWO wild THREE car, FOUR willed (transplanting the LE). (This would appear in the solution list as “c(le)ar, wil-d.”) Another example: ger(ry)mander, car-away.

The heart transplant was invented by Xemu and introduced in June 1997.