The most common and most likely answer to this crossword clue is the 5 letter word APING
I've seen this crossword clue in The Daily Telegraph
A
P
I
N
G
More clues leading to the result APING
- Copying fastener in silver
- A test for internet connection is taking off
- Copying brooch in silver
- A sharp noise that’s echoing
- A report of nearby sub taking off
- Imitating a sound on the microwave?
- Copying a sound made by computer
- Imitating the sound of a bullet?
- A warning sound perceived in taking off
- Copying recording but missing start
Buddy explains!

The straight part
We know that "taking off" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case taking off = aping.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 APING mean?
APING verb- To behave like an ape.
- To imitate or mimic, particularly to imitate poorly.
- Foolish imitation or mimicry.