The most common and most likely answer to this crossword clue is the 1 plus 4 letter word E COLI
I've seen this crossword clue in The Guardian
E
C
O
L
I
More clues leading to the result E COLI
- European firm initially looks into bacteria in canal
- Harmful thing, priest inhaling carbon monoxide
- Bug, green, with large head on it
- Environmental ills half disposed of when reversing bacterial species
- Half of line covered by green bacteria
- Foremost of experts consulted on lingering infection source
- Green, Philip’s heart uplifted — that might make you sick
- Tablet reduced abdominal pain — possible cause?
- Germ gets you ending with the stomach ache, mostly
- What may be found in the gut in ulcerative colitis
Buddy explains!
The straight part
We know that "Cause of infection/Cause of infection" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case cause of infection/cause of infection = e coli.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.