are you refering to the glass of the tank? not sure what your refering too there....if you mean the outside, then, yes, clean it..What i always do is put some glass cleaner on a cloth in a sperate room from the tank because if you spray it at the tank, particles of the cleaner are going to end up going in to the tank..which is what we DONT want...even though you have no fish in there at the moment, it gets you into good practice for when your up and running..
If your refering to something completly different, shout up mate.,.
Niko
Niko