The most common and most likely answer to this crossword clue is the 2 plus 3 plus 3 letter word ON THE JOB
O
N
T
H
E
J
O
B
More clues leading to the result ON THE JOB
- Busy hospital in Eton cured one patient
- Busy hospital in Eton treated one patient
- John to be working thus?
- Working only briefly, the Jones boy getting confused
- Busy doctor not male, with one patient?
- A certain book keeps half of them busy
- Doctor not male — one patient at it
- John to be trained at work
- Working at article with patient one described in book
- No going back with article by patient man at work
Buddy explains!

The straight part
We know that "Working" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case working = on the job.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 ON THE JOB mean?
ON THE JOB adjective- (of training) obtained whilst working