Fighting

[Avodroc13]

Can I play a sorcery to cause a defender to fight another creature? Defenders can't attack, but fighting due to a sorcery isn't attacking.

(I'm talking about a green card for 1 mana that states target creature you control fights target creature your opponent controls. Not sure what the name of it is though.)

[Rasser]

 {Prey Upon}
Yes

701.10a: A spell or ability may instruct a creature to fight another creature or it may instruct two creatures to fight each other. Each of those creatures deals damage equal to its power to the other creature.

701.10d: The damage dealt when a creature fights isn't combat damage.

[Avodroc13]

Awesome, thanks for the prompt reply.

[Pleeb]

The defender ability doesn't change the fact that is a creature. If the spell is going to discriminate against a creature with a certain ability or trait, it will explicitly say so in the text of the spell.