The most common and most likely answer to this crossword clue is the 4 letter word NASA
N
A
S
A
More clues leading to the result NASA
- Huge agency makes a hospital suffer a setback
- A hospital rejected rocket scientists
- Women as astronauts? Some here
- North America and South America’s space agency
- Continents combine to create an agency with responsibility over the entire Earth, and beyond
- Far-flung travel agency picked up old colonel from Egypt
Buddy explains!

The straight part
We know that "space agency" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case space agency = nasa.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.