"Exhaust this card while attacking a figure that has suffered damage to apply +1damage to the attack results."

If a creature is attacking a figure that has not suffered any damage yet, doesn't the feeding frenzy effect not apply since it says while attacking and damage is not calculate until step 7 of the attack? Damage from feeding frenzy would have to be applied before step 7 and that figure would have no damage yet?

Yes, the target figure needs to have suffered damage before the attack.

Feeding Frenzy adds +1 damage to the attack results during step 4: Apply Modifiers, if the target figure has suffered damage.

(Also note that the damage is added to the attack pool, it can be blocked by defense.)