Change one letter, make a new word

[BonnieShels]

Waniker - when someone refers to "that w@nker", "that pr*ck" etc everyone immediately knows who is being talked about.

[OwlsFan]

Piles - a right pain in the ars'

[nigel-harps1954]

Blandishes - When an away fan whips out a new flag or banner on match day and it just isn't to your taste

[Eminence Grise]

Brayzenly - the optimum way of bringing the League of Ireland into disrepute.

[Eminence Grise]

Some good ones at this link - 'askhole' had me snorting out loud! - even though some have more than a single letter change.

http://www.demilked.com/new-modern-funny-random-words-portmanteus/

[SkStu]

Sorry...just seeing this now. As in moniker

[stann]

Second one is a couple of letters, only one syllable though...

Brill - A restaurant tab that, when it arrives, is not nearly as big as you expected
Mozery - Your state of mind when "There Is A Light That Never Goes Out" says everything to you about your life.
Munce - Mince that's been in the fridge for a while...

[Eminence Grise]

A nincomplete - one of my students who hands me up two-thirds of their work, and still thinks they're going to get a good grade.

[Eminence Grise]

Meanderthal – a creature who shuffles out in front of traffic to ramble across the street. May act surprised at the presence of cars and mutter bestial sounds when challenged by drivers.

[OwlsFan]

Piles, someone who has been an pundit for so long that he's developed hemorrhoids from sitting on his backside.

[OwlsFan]

Yule, a sort of donkey which only appears in Christmas plays.

[Eminence Grise]

Adminton.

A game where a heavy bureaucracy challenges you to deal with more and more things served up to you.

Yep, it's one hour into Monday morning and already the inbox is overheating. Good job I have this site for avoidance strategies!