Ship requires check-in before this (8)
I believe the answer is:
schooner
'ship' is the definition.
(I know that schooner is a type of sailships)
'check-in before this' is the wordplay.
'check' becomes 'ch' (abbreviation).
'in' means one lot of letters goes inside another.
'before this' becomes 'sooner' (before the current time).
'ch' placed into 'sooner' is 'SCHOONER'.
'requires' is the link.
(Other definitions for schooner that I've seen before include "Old sailing ship and tall sherry glass" , "A measure or glass for sherry" , "Sailing vessel - drinking vessel" , "boat" , "wooden vessel" .)