Hopeless Irish sunburned sailor in melee at sea (12)
I believe the answer is:
irredeemable
'hopeless' is the definition.
(I've seen this before)
'irish sunburned sailor in melee at sea' is the wordplay.
'irish' becomes 'IR' (abbreviation for Irish).
'sunburned' becomes 'red' (I've seen this in another clue).
'sailor' becomes 'ab' (abbreviation for able seaman).
'in' is an insertion indicator.
'at sea' indicates anagramming the letters.
'melee' anagrammed gives 'eemle'.
'ab' going within 'eemle' is 'eemable'.
'ir'+'red'+'eemable'='IRREDEEMABLE'
(Other definitions for irredeemable that I've seen before include "Not able to be saved" , "Without a pawn ticket, things can be so" , "hopeless" , "Beyond being saved" .)