The most common and most likely answer to this crossword clue is the 4 plus 3 letter word TAKE OFF
I've seen this crossword clue in The Daily Telegraph
T
A
K
E
O
F
F
More clues leading to the result TAKE OFF
Buddy explains!
The straight part
We know that "Become popular/mimic" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case become popular/mimic = take off.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 TAKE OFF mean?
TAKE OFF noun- The rising or ascent of an aircraft or rocket into flight.
- A parody or lampoon of someone or something.
- A quantification, especially of building materials.
- The removal of sheets from the press.
- The spot from which one takes off; specifically, the place from which a jumper rises in leaping.