Parry is 2 + half martial arts.
If the combat is not trained, the combat skill is 0, although you would roll like any untrained skill when you make a combat throw.
A character with untrained battles has Parry 2. By the way, this is the same as parrying an inanimate object, like a brick wall.
This is in the rulebook, First chapter: Character creationunder Trains, For the stream Wild Worlds Deluxe Rules, that's on page 17.
Parry equals 2 plus half of your character's battle (2 if a character has no fight) as well as any bonuses for shields or certain weapons. This is the target number (TN) to hit your hero in close combat.