Attention: boat swallowed by sea will be set aside (9)
I believe the answer is:
earmarked
'set aside' is the definition.
(I've seen this before)
'attention boat swallowed by sea' is the wordplay.
'attention' becomes 'ear' (having someone's ear is having their attention).
'boat' becomes 'ark' (ark is a kind of boat).
'swallowed by' is an insertion indicator.
'sea' becomes 'med' (abbreviation of Mediterranean).
'ark' inserted inside 'med' is 'marked'.
'ear'+'marked'='EARMARKED'
'will be' is the link.
(Other definitions for earmarked that I've seen before include "appearance of one who underwent piercing?" , "Reserved, set aside" , "Distinguished" , "Put by for later" , "Carefully chosen" .)