The most common and most likely answer to this crossword clue is the 6 letter word DUCKED
I've seen this crossword clue in The Guardian
D
U
C
K
E
D
More clues leading to the result DUCKED
Buddy explains!

The straight part
We know that "failed to answer" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case failed to answer = ducked.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 DUCKED mean?
DUCKED verb- To quickly lower the head or body in order to prevent it from being struck by something.
- To quickly lower (the head) in order to prevent it from being struck by something.
- To lower (something) into water; to thrust or plunge under liquid and suddenly withdraw.
- To go under the surface of water and immediately reappear; to plunge one's head into water or other liquid.
- To bow.
- To evade doing something.
- To lower the volume of (a sound) so that other sounds in the mix can be heard more clearly.
- To enter a place for a short moment.