Cryptic crossword clue
Fuel for warships in part of earth that’s covered 7

The most common and most likely answer to this crossword clue is the 7 letter word SUBSOIL

I've seen this crossword clue in The Guardian
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Buddy explains!

The straight part
We know that "part of earth that’s covered" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case part of earth that’s covered = subsoil.
The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.
This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.

What does SUBSOIL mean?

SUBSOIL noun
  1. The layer of earth that is below the topsoil.
SUBSOIL verb
  1. To turn up the subsoil of.

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