Answer:

ink

Answer	Crossword Clue
INK	Sign, as a contract
INK	Squid juice
INK	Writing fluid

INK	Calamari ejection
INK	Cephalopod's defense
INK	Invisible ..
INK	Press coverage
INK	Shirt-pocket stain, often
INK	Sign
INK	Sign up
INK	Squid secretion

INK	Printing need
INK	Publicity
INK	Tattoo artist's needleful
INK	Staples purchase
INK	Tattoo artist's need
INK	Plume dip
INK	Prepare a press
INK	Onetime well content

INK	Well contents?
INK	Contents of a well
INK	Squid squirt
INK	Octopus defense
INK	Tattooist's supply
INK	Well contents
INK	Squid fluid
INK	Squid's defense

INK	Substance expelled by cuttlefish
INK	Make official, in a way
INK	Newspaper coverage
INK	Press coverage, slangily
INK	Fingerprinting need
INK	It comes from a well
INK	Publicity, slangily
INK	Old school desk's supply

INK	Pen filler
INK	Cuttlefish camouflage
INK	Octopus' output
INK	Publicity, in slang
INK	Bic filler