I have to send my passport for some administrative task.
Can you be more specific? For example, are you applying for a UK driving licence?
I wonder if I lose passport, I can get duplicate from my home country's embassy.
Yes, exactly that. How long it would take to get a replacement passport would depend upon which country we are talking about.
But what will happen to UK FLR stampings? Do I have to pay FLR fee again to get stamping done???
Yes, you would need to make application for the visa to be put into the new passport. Except, for example, if that old visa is just about to expire, you might not bother to get the old visa put into the new passport, but instead wait until you apply for the new visa to be put into your new passport.
General point ... in a sense the visa is in two places ... your passport and the IND computer system. So losing the passport does not mean the visa is lost. It continues and it is possible to get it put into a replacement passport.