Can't Parse One In The Guardian Prize

[Orthrus]

As is so often the case, I've finished the Guardian Prize (#28,356), but I can't parse 1D:

Diet of mostly odd junk? (4,4) _A_T _O_D

I have FAST FOOD - can someone explain it?

[Bonefixer1]

Diet = fast
Of + most of ‘odd’ gives food?

[Toorak]

Fast (diet) & anagram of ‘of od(d)’

[Orthrus]

I thought that was it, but couldn't see an anagram indicator.

Unless DIET and JUNK are both on &Lit duty.

[Toorak]

I think it’s an &lit with junk as the anagram indicator