First to leave ship lane (5)
I believe the answer is:
alley
'lane' is the definition.
(I know that alley is a type of lane)
'first to leave ship' is the wordplay.
'first to leave' means to remove the first letter (the first letter leaves).
'ship' becomes 'galley' (I've seen this before).
'galley' with its first letter taken off is 'ALLEY'.
(Other definitions for alley that I've seen before include "Back lane" , "Passage between buildings" , "Marble" , "Bowling lane" , "Walk" .)