a lot of times if u clean bulk right, you can actually reduce your bf% at the same time as your gaining lean mass, so while the scale may say your weight is not chainging, in reality you could be losing fat poundage, and putting on lean mass poundage
very brief guidlines:
1. eat small meals through out the day, prefibly 6-8 (this is a given, if you don't know this much you shouldn't be reading anabolic minds)
2. for the most part you want to seperate your fat and carbs during meals, for example meal 1: primarily carbs + protein, following meal fats + protien with minimized carb intake, etc.
3. what ever your calorie intake is right now, start by increasing by 250-500 calories a day, eat this same amount of calories for about 2 weeks, after 2 weeks access your bf% and the scale
4. If its working, continue for another 2 weeks, if you've stalled, increase calorie intake again by 250 calories a day.
By increasing calorie intake slowly, your allowing your metabolism to adapt. Thus resulting, in a progessive gain in lean muscle mass. Often times, people who want to start a clean bulk will increase calorie intake overnight by 1000 calories. Regardless of how your eatting, the mass quantity in calorie intake is very likely to result in fat gain.
Although this method may seem very slow, it is by far the most realistic and productive way to clean bulk
Do this for a good three months, and you will be rewarded with decent lean mass gains, and most likely a lower bf%
for more details on this method
read John Beardi's Massive Eatting series over at t-nation