Like a "wet" signature

INPEN

Think of how you might sign a document digitally instead of with ink.

The clue plays on the idea of a "wet" signature, which traditionally means a handwritten one made with ink (as opposed to a digital signature). "In pen" sounds like "in pen" but is written as "INPEN" to mimic how you'd describe signing something by hand—literally putting ink to paper. The wordplay hinges on interpreting "wet" as ink-based and turning the phrase into a compact, slightly altered form. It’s a clever way to hint at the answer while keeping the surface meaning straightforward.