Ignorant Oscar is abandoning state for sea (3-8)
I believe the answer is:
ill-informed
'ignorant' is the definition.
(I've seen this before)
'oscar is abandoning state for sea' is the wordplay.
I cannot quite understand how this works, but
'oscar' could be 'o' (phonetic alphabet: alpha, bravo, charlie etc.) and 'o' is present in the answer.
'state' could be 'ill' (ill is a kind of state) and 'ill' is found in the answer.
'sea' could be 'med' (abbreviation of Mediterranean) and 'med' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
(Another definition for ill-informed that I've seen is " ignorant".)