Defending a fire elemental to death

[hcobb]

Plan is to choose the defend option to greatly increase the chance the Fire elemental will roll a critical failure and thereby inflict 1d6 damage on itself.

But can you defend yourself when "Ordinary weapons do not affect this creature of living fire" (ITL 87)? (Note that the word is affect, not damage here.)

Of course there's no question that a wizard's staff could be used.