Believe it or not, this is the normal scene when someone looks here for the first time. Its an accumalation of oil vapour from years of driving.
Disconnect the battery. Disconnect the throttle body plug. Undo the screws that hold it on and give it a damn good clean out with some carb cleaner. You can't damage anything ulness you drop it so don't worry about anything. Once nice and clean, pop it back on, the sealing rubber is reusable. Fitting is the reverse of above.
Connect it all back up, reconnect the battery and turn the key. You'll probably find the revs will be a bit high for 10 seconds or so but it will settle straight away.
Job done.
;-)