Backing lost for nosy US agency (4)

I believe the answer is:

nasa

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'agency' is the definition.
Both the definition and answer are singular nouns.
Perhaps you can see an association between them that I can't see?

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for nasa that I've seen before include "rocket launcher" , "US agency responsible for space flight" , "US headquarters for space exploration" .)

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