The most common and most likely answer to this crossword clue is the 4 plus 5 letter word WAGE SLAVE
I've seen this crossword clue in Financial Times
W
A
G
E
S
L
A
V
E
More clues leading to the result WAGE SLAVE
Buddy explains!

The straight part
We know that "I can’t not work" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case i can’t not work = wage slave.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.