The most common and most likely answer to this crossword clue is the 6 plus 9 letter word ROCKET SCIENTIST
I've seen this crossword clue in The Daily Telegraph
R
O
C
K
E
T
S
C
I
E
N
T
I
S
T
More clues leading to the result ROCKET SCIENTIST
- Stick insect tore about, the clever chap
- Expert sorts nice ticket for play
- A high-flier who launches one studying salad?
- A high achiever, I launch farreaching studies
- Broadcast of cricket test is on, clever clogs
- Very clever person notes it’s cricket to be played
- Boffin succeeded in tricks to entice criminal
Buddy explains!
The straight part
We know that "Very clever person" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case very clever person = rocket scientist.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.