The most common and most likely answer to this crossword clue is the 4 plus 3 letter word LIFT OFF
I've seen this crossword clue in The Daily Telegraph
L
I
F
T
O
F
F
Buddy explains!

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 LIFT OFF mean?
LIFT OFF noun- The point in the launch of a rocket or an aircraft where it leaves contact with the ground.
- The point at which a person or animal leaves the ground, as for example when jumping.