The most common and most likely answer to this crossword clue is the 6 letter word GRIPPE
I've seen this crossword clue in The Daily Telegraph
G
R
I
P
P
E
More clues leading to the result GRIPPE
- Complaint about onset of Parisian flu
- Almost caught flu
- Complaints: this old one, another about parking
- Doctor with bandage’s last to cover gash’s infection
- End of leg split on exercise producing infection
- Influenza under control? Almost
- Complain about onset of pig flu
- One of the illnesses that are catching, you say
- It's an old fashioned disease to complain about pressure
- Complain about onset of pneumonia, or flu?
Buddy explains!

The straight part
We know that "Influenza" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case influenza = grippe.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 GRIPPE mean?
GRIPPE noun- Influenza, the flu.