The phrase "little sun" refers to a small or tiny version of the sun, which is the massive and bright star that gives light and heat to our planet. Full definition
It's north - facing, so gets very little sun. (idealhome.co.uk)
Too much sun obviously is bad for you with the threat of skin cancer; but too little sun can make you vitamin - D deficient, which has been linked with various diseases. (pranamarvillas.com)
The roof has little sun exposure because it faces the north and is protected with vegetation. (treehugger.com)