A father was talking to his daughter about always defending her actions. It is a nice mashup of “dressed to the nines” (wearing very elegant or formal clothes) and “defend to the death your right to say (something)” (disapprove what another is saying but allow them to say it). “Dressed to the nines” expression is thought to have originated from the 99th Wiltshire Regiment, a military unit noted for its smart appearance.
This one reminds me of the classic I posted a few years ago: “She was dressed to a tee (or t)”. https://malaphors.com/2014/01/21/he-was-dressed-to-a-tee-or-t/
A big thanks to Mike Kovacs, Chief Malaphor Reporter, for hearing this one.