The most common and most likely answer to this crossword clue is the 6 letter word TROJAN
I've seen this crossword clue in Financial Times
T
R
O
J
A
N
More clues leading to the result TROJAN
- Month after end of contract, row not finished for hard worker
- Hard worker heartless janitor’s thrown out
- It corrupts data of half the company at start of the year
- Hard worker wants jar – not pissed
- Tredegar’s vergers love month in Paris for instance
- determined fellow
- Dedicated worker taking time over wine, new one being rejected
- Exemplary worker from the city of Paris
- Seen in bistro, January’s ‘most industrious worker’
- Hard worker in Paris, say
Buddy explains!

The straight part
We know that "Paris for instance" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case paris for instance = trojan.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 TROJAN mean?
TROJAN noun- Malware that appears to perform or actually performs a desired task for a user while performing a harmful task without the user's knowledge or consent.
- To infect (a system) with a trojan.
- Describing a satellite (moon or minor planet) that shares an orbit with another