King disembarks from boat to eat away (4)
I believe the answer is:
etch
'to eat away' is the definition.
(I've seen this before)
'king disembarks from boat' is the wordplay.
'king' becomes 'K' (abbreviation for king in chess).
'disembarks from' suggests deleting specific letters.
'boat' becomes 'ketch' (ketch is a type of sailing boat).
'ketch' with 'k' removed is 'ETCH'.
(Other definitions for etch that I've seen before include "Use acid to cut design" , "Delineate" , "Make incisions" , "Cut; engrave" , "Corrode" .)