Keep sea vessel outside area (8)
I believe the answer is:
maintain
'keep' is the definition.
(I know that keep can be written as maintain)
'sea vessel outside area' is the wordplay.
I cannot really see how this works, but
'sea' could be 'main' (synonyms) and 'main' is located in the answer.
'area' could be 'a' (maths abbreviation) and 'a' is found in the answer.
'vessel' could be 'tin' (type of container) and 'tin' is found in the remaining letters.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for maintain that I've seen before include "Profess" , "Keep (at the same level)" , "Keep in good order" , "Keep up - carry on" , "Keep - support" .)