The most common and most likely answer to this crossword clue is the 8 letter word MESSMATE
I've seen this crossword clue in The Guardian
M
E
S
S
M
A
T
E
More clues leading to the result MESSMATE
- Naval colleague met seas running around head in Morocco
- Fellow diner putting hot water on tea
- Trouble, with divine Greek lady overwhelming married friend
- Food from Eton — tucked in after male fellow diner
- Confusion leads to victory for fellow sailor perhaps
- Trouble with maiden worried eating companion in army
Buddy explains!

The straight part
We know that "friend" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case friend = messmate.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 MESSMATE mean?
MESSMATE noun- An associate with whom one shares a mess (eating place) on a ship
- Any of various eucalypts with rough bark, specifically Eucalyptus obliqua.