The most common and most likely answer to this crossword clue is the 5 letter word DEEPS
D
E
E
P
S
Buddy explains!

The straight part
We know that "Oceans" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case oceans = deeps.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 DEEPS mean?
DEEPS noun- (with "the") The deep part of a lake, sea, etc.
- (with "the") A silent time; quiet isolation.
- A deep shade of colour.
- The profound part of a problem.
- (with "the") The sea, the ocean.
- A fielding position near the boundary.