The most common and most likely answer to this crossword clue is the 6 letter word DRIVEL
I've seen this crossword clue in The Guardian
D
R
I
V
E
L
More clues leading to the result DRIVEL
- Line on chauffeur’s pants
- Cobblers urge beginning with last
- Nonsense, being forced to replace name with learner
- Foolishness of motorist changing hands
- Labour leader getting behind campaign for tripe
- Doctor left to collect Arachne’s eyewash
- Bull and steer on left
- Foolish talk of club finally changing hands
- It makes no sense to push learner
- Nonsense from learner following ambition
Buddy explains!

The straight part
We know that "Foolishness" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case foolishness = drivel.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 DRIVEL mean?
DRIVEL noun- Senseless talk; nonsense
- Saliva, drool
- A fool; an idiot.
- To have saliva drip from the mouth; to drool.
- To talk nonsense; to talk senselessly; to drool.
- To be weak or foolish; to dote.
- A servant; a drudge.