This is a play on two words. "Muck" and "Makeover." A makeover where everything is slathered on in a great rush.
Basically it is a makeover, but done in such a tremendous hurry or with little regard to finesse because of limited time where the one being made over may not be at all appealing to most, but is just fine for someone desperate for a date or will take anyone of the opposite sex as they are.
"Janice, Horchester is going to be here in an hour for the dance !"
"Oh my god, I look awful, what will I do ?"
"Don't worry, we'll give you a muckover. You'll be fine."