Policy threat to both government and opposition? (5,5)
I believe the answer is:
third party
'opposition?' is the definition.
The definition and answer can be both people as well as being singular nouns.
Perhaps there's a link between them I don't understand?
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for third party that I've seen before include "Person besides the two primarily involved" , "Someone other than the principals" , "Liberals once?" , "Another (uninvolved) person" , "Person not directly involved" .)