Each of the feeder answers clues a word which is one letter off from "SPAM" followed by something - in particular, a letter in "SPAM" is changed. When you interpret the phrase "SPAM something" as a description of something that you are spamming, they each match up with one of the given situations.
|Feeder||Clued Phrase||Situation||Spam Phrase||Extracted Letter|
|MATCH OF THE CENTURY||SPASSKY||...When you're painting scenery||SPAM SKY||S|
|TAILOR||SEAMSTRESS||...When you're writing poetry||SPAM STRESS||E|
|CORPORAL PUNISHMENT||SPANKING||...When you're playing checkers||SPAM KING||N|
|EMBOSSING||STAMPING||...When someone ignores you||SPAM PING||T|
|THREE HUNDRED||SPARTAN||...When you're doing math||SPAM TAN||R|
|BENJAMIN TALLMADGE||SPYMASTER||...When you're planting||SPAM ASTER||Y|
Taking the changed letters in the order of the situations spells the answer SENTRY.