The meaning of this noun is the same as the kanji, lamp. Can also mean light and torch as well, depending on where you herald from.
The reading is like that of 明るい, which means "bright." At least the あか part is the same. What is a lamp if not 明るい (あか)? Another way to think of it is "what is a bright color?" The color 赤 (あか) is a bright color and would make a sexy lamp.
There was only a little candle light in the room.