The most common and most likely answer to this crossword clue is the 4 plus 9 letter word CAPE CANAVERAL
C
A
P
E
C
A
N
A
V
E
R
A
L
More clues leading to the result CAPE CANAVERAL
Buddy explains!
The straight part
We know that "rocket launch site" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case rocket launch site = cape canaveral.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.