The most common and most likely answer to this crossword clue is the 7 letter word SPITTLE
I've seen this crossword clue in Independent
S
P
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More clues leading to the result SPITTLE
Buddy explains!

The straight part
We know that "bodily fluid" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case bodily fluid = spittle.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 SPITTLE mean?
SPITTLE noun- Spit, usually frothy and of a milky coloration.
- Something frothy and white that resembles spit.
- Spit-up or drool of an infant.
- A charitable house to receive and care for sick people, later distinguished from a hospital as being especially for those of a low class or meagre financial means.
- A small sort of spade.
- To dig or stir with a small spade.