Sailor forgetting pop on ship: might one go on the lash? (8)
I believe the answer is:
eyeliner
But I can't explain it at all! Could you help me understand?
(Other definitions for eyeliner that I've seen before include "Item of 25dn" , "Cosmetic pencil" , "Type of make-up" , "Makeup for the peepers" , "highlight for look-out" .)