I know! What does it mean?
Q has used this phrase before; https://qanon.pub/#572 (#572), https://qanon.pub/#1440 (#1440); https://qanon.pub/#2084 (#2084), https://qanon.pub/#1760 (#1760). It is associated with the phrase Dark to light.
Enemy @ the Front Door is unclear; there was a Brit tv series Enemy at the Door, seems unlikely.
USSS 'stay' alerts prevent travel might refer to the assassination attempt on French leader Macron - 'USSS' obviously United States Secret Service.
There are a bunch of short Q posts all using the pharase [Placeholder ...]