The most common and most likely answer to this crossword clue is the 3 plus 6 letter word TOP BANANA
T
O
P
B
A
N
A
N
A
More clues leading to the result TOP BANANA
- Leader, first of those on hand?
- Boss to lead with article, followed by stories
- Chief has to lead with three articles
- Chief, best of the bunch?
- An ace in the hand?
- Number One hit about Scottish holiday spot — one providing haven for Paul originally
- Leader to lead with three articles
- Star who’s the pick of the bunch?
- Most important person to lead America? Idiot!
- Leader has to lead a fool
Buddy explains!

The straight part
We know that "number one" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case number one = top banana.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.