Another one that stumped me. But, in retrospect, I must have just not really been paying attention.
It's not 广 on top.
In looking at it, this is somewhat of a confusing case. The pronunciation of the character (lu3) is quite close to the pronunciation of the radical (hu3), and dissimilar to the pronunciation of the "phonetic" part (nan2).
And the meaning really has nothing, as far as I can see, to do with a tiger.
In the simplified form, 虏, the phonetic part, 力, has a pronunciation (li4) closer to that of the character. Although, in my opinion, 力 is a much more meaningful radical for the character than 虍 is.