Hey @Kermit, I'd be keen to hear what you've already tried.
I've been able to clear a drain with some light plunging in cold water followed by a flush of boiling water before, but some heavier blockages may need a specialised drain cleaner. I've found a gel at Coles that works super well, but the name is escaping me right now (I know the bottle is pink). Anyway, I'd say try the plunger/flush combo first and if that doesn't work I'd hit it with some drain cleaning gel. After pouring the gel down the drain, you wait around 10 - 15 minutes and then flush it with warm water. Just make sure you don't combine these two methods, flushing the drain cleaner with boiling water will end in a bad, bad time. Oh, and make sure you wear rubber gloves for all of this.
If both of these methods fail, it might be time to call a plumber.
