The most common and most likely answer to this crossword clue is the 5 plus 3 plus 4 letter word SWING THE LEAD
I've seen this crossword clue in The Guardian
S
W
I
N
G
T
H
E
L
E
A
D
More clues leading to the result SWING THE LEAD
Buddy explains!
The straight part
We know that "Way to avoid duty at sea" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case way to avoid duty at sea = swing the lead.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.