The most common and most likely answer to this crossword clue is the 9 letter word LAZYBONES
I've seen this crossword clue in Financial Times
L
A
Z
Y
B
O
N
E
S
More clues leading to the result LAZYBONES
Buddy explains!
The straight part
We know that "Shirker" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case shirker = lazybones.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 LAZYBONES mean?
LAZYBONES noun- A person who is lazy; one who is inactive and without ambition.