The most common and most likely answer to this crossword clue is the 17 letter word TRISKAIDEKAPHOBIA
T
R
I
S
K
A
I
D
E
K
A
P
H
O
B
I
A
Buddy explains!
The straight part
We know that "fear, covering this number" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case fear, covering this number = triskaidekaphobia.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 TRISKAIDEKAPHOBIA mean?
TRISKAIDEKAPHOBIA noun- Fear or dislike of the number thirteen (13).