Tattooing fluid (3)
I believe the answer is:
ink
'tattooing fluid' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for ink that I've seen before include "Material used in printing" , "Cuttlefish's secretion" , "Pen's contents" , "Liquid in pens" , "Liquid from a squid" .)