First, before you even start using Cycles it’s good to know what exactly happens when you render: Camera (!) shoots out some ray tentacles to check where it has to reach and where not. It happens not knowing anything about the scene, randomly. If ray hits something it reflects according to optical laws, some information is stored about what got hit Diffuse, Glossy or Light source. Next reflected path is analysed similarly and so on - times you set in sampling.
Now, since lamps are not visible directly in your image Cycles has a hard time getting some random ray out of the Camera hit the asphalt (Diffuse, reflection ray will start in a widely random directions) reflect and hit the lamp. Cycles is severely ‘dumb’ in finding small light bulbs just by reflected rays. Also ‘random’ is a quite limited amount compared to what mother nature can afford (trillions of rays hitting each surface). ‘Random’ might repeat itself in calculations - as a result you get these fireflies - rays more than often travel same directions and bring back lighting information in one pixel range where this value accumulates.
Such information brightens your monitor up to the limits - file where information is stored can keep much higher values however.
Here Clamp starts to play - if you set it less than 1 (=value your monitor is able to display) you get overall darkened image, if you set clamp to 10 this will limit maximum values of light to 10. Setting Clamp to 0 does switch off this mechanism.
Clamp is not a universal cure to fireflies - idea behind is if you want to use image containing bright pixels in compositing, such values ‘damage’ image mixing calculations, bring in further distortions.
This all was to “I’ve 10 set in clamping direct and indirect and doesn’t seem to make any difference”. Details -> RTFM.
Have you read anything about how human eye perceives light, what are differences between “dark” and “bright”, what does colors look like in the midday and during the full Moon? Check out and try making midday into the midnight using Blender’s compositing or any other image editor.