The most common and most likely answer to this crossword clue is the 9 letter word ERGOMETER
E
R
G
O
M
E
T
E
R
Buddy explains!

The straight part
We know that "It shows you the amount of work done" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case it shows you the amount of work done = ergometer.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 ERGOMETER mean?
ERGOMETER noun- A dynamometer used to measure the work done by muscles
- A rowing machine or ergocycle