The most common and most likely answer to this crossword clue is the 6 letter word JOULES
J
O
U
L
E
S
More clues leading to the result JOULES
Buddy explains!

The straight part
We know that "work units" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case work units = joules.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 JOULES mean?
JOULES noun- In the International System of Units, the derived unit of energy, work and heat; the work required to exert a force of one newton for a distance of one metre. Also equal to the energy of one watt of power for a duration of one second. Symbol: J