Can she ruin a U.S. federal agency? (6)
I believe the answer is:
marcia
'federal agency?' is the definition.
The definition suggests a singular noun which matches the answer.
'can she ruin a u s' is the wordplay.
I cannot really see how this works, but
'she' could be 'marci' and 'marci' is located in the answer.
'a' is found in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Another definition for marcia that I've seen is " Woman".)