The most common and most likely answer to this crossword clue is the 7 letter word CONGEST
I've seen this crossword clue in The Guardian
C
O
N
G
E
S
T
More clues leading to the result CONGEST
Buddy explains!
The straight part
We know that "clog" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case clog = congest.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 CONGEST mean?
CONGEST noun- (history) a farmer whose lands do not support him adequately.
- To hinder or block the passage of something moving, for example a fluid, mixture, traffic, people, etc. (due to an excess of this or due to a partial or complete obstruction), resulting in overfilling or overcrowding.