The most common and most likely answer to this crossword clue is the 5 letter word CLUMP
I've seen this crossword clue in The Guardian
C
L
U
M
P
More clues leading to the result CLUMP
Buddy explains!

The straight part
We know that "Clot" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case clot = clump.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 CLUMP mean?
CLUMP noun- A cluster or lump; an unshaped piece or mass.
- A thick group or bunch, especially of bushes or hair.
- A dull thud.
- The compressed clay of coal strata.
- A small group of trees or plants.
- A thick addition to the sole of a shoe.
- To form clusters or lumps.
- To gather in dense groups.
- To walk with heavy footfalls.
- To strike; to beat.