How do you clean the black scrum that comes from the washer

The water goes into the compartments in the tray by a filter in the top. This gets blocked by water scrum and detergent build up. Remove the powder drawer and clean inside the cavity. Also, clean the drawer....especially the conditioner section, as the syphon can get clogged up and cause a premature syphon

uncontested scrum Google Search

Usually, you can study online. What learning institution are you wanting to study from?

john low temperatures washing can cause the machine to smell
if it was me i would set the machine to it's hottest wash and use a descaller or bleach and washing liquid ,after wash has finished give it an extra rince cycle./ scrum around rubber seal behind door before starting wash. check pump filter is clean,

that most likely is coming from the tub seals and not dirt under the agitator,the tub seals are made from black rubber and metal.send the model number off of the washer or go to this site and look up your machine and it will have a breakdown on the agitator and you can see how to get it out.
http://www.searspartsdirect.com/partsdirect/index.action

I was able to find for you a great definition of a scrum from the Washington State women's rugby organization website. They define a scrum as:
"This is the most unique aspect of rugby (see our pictures page for a visual). It consists of the eight forwards on both teams and occurs after a rule infraction such as a forward pass. Essentially what happens is the eight players bind on to one another while the front row binds on to the other team. The two packs then push on each other while the ball is thrown in by the team which was not responsible for the penalty. The ball is then heeled (kicked backwards) by the forwards until it pass through the back of the scrum."

For more useful rugby info, check out their site: http://womensrugby.wsu.edu/faq.aspx

You need to chjeck and clean the pump filter.
Remove rear panel of washer.
Locate and remove the large black hose fastened to bottom of drum.
Remove and clean plastic filter inside hose.
Reassemble and test.

Black stains could only come from rubber part that is deteriorating. Need to check all hoses, rubber boot and at bearing seal.