Lost operation base, scuttled on the Black Sea (10)
I believe the answer is:
sebastopol
'black sea' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'lost operation base scuttled on' is the wordplay.
I cannot quite understand how this works, but
'lost' could be 'l' (abbreviation in sporting league tables) and 'l' is located in the answer.
'operation' could be 'op' and 'op' is located in the answer.
an anagram of 'base' is 'seba' which is present in the answer.
'on' could be 'to' and 'to' is found in the answer.
A single letter 's' remains which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
'the' is the link.
Can you help me to learn more?
(Other definitions for sebastopol that I've seen before include "Crimean port" , "Ukrainian port" .)