The most common and most likely answer to this crossword clue is the 5 letter word GERMS
I've seen this crossword clue in The Daily Telegraph
G
E
R
M
S
More clues leading to the result GERMS
- Causes of disease resistance in cat’s eyes, perhaps
- About to back blocking MSG fermented bacteria
- Beginnings of grisly epidemic rats might spread
- People in Berlin failing to grasp an infection source?
- Mid-Europeans without an agency for infections?
- Shoots Europeans after article is censored
- About royal jewels, they’re sickening
- Jewellery clasping tip of finger is a source of infection
- Shoots shell from gunwale on ship
- Source of infection right inside bits of 9?
Buddy explains!
The straight part
We know that "infection source" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case infection source = germs.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 GERMS mean?
GERMS noun- The small mass of cells from which a new organism develops; a seed, bud or spore.
- A pathogenic microorganism.
- The embryo of a seed, especially of a seed used as a cereal or grain. See Wikipedia article on cereal germ.
- The origin of an idea or project.
- An equivalence class that includes a specified function defined in an open neighborhood.