The most common and most likely answer to this crossword clue is the 6 letter word PRAWNS
I've seen this crossword clue in The Sunday Telegraph
P
R
A
W
N
S
More clues leading to the result PRAWNS
Buddy explains!

The straight part
We know that "Seafood" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case seafood = prawns.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 PRAWNS mean?
PRAWNS noun- Pornography.
- (chiefly in the plural) A pornographic work.
- Material, usually visual, presenting something desirable in a sensational manner.
- Material that provides illicit gratification of an obsessive or unhealthy interest in something.
- A crustacean of the suborder Dendrobranchiata.
- A crustacean sometimes confused with shrimp.
- A woman with a very toned body, but an unattractive face.
- A fool, an idiot.
- To fish for prawns.