You can do Fajr then pray witr as qadha. Salaatul Witr is mustahab and all the parts of it are mustahab.
So you have two options either you can do Salaatul Witr with just Fatiha and Ikhlas, Ruku and sujood if there’s time for just that or you can do Fajr and then pray Witr as qadha