Tangerines were a type of citrus fruit found on Earth. Similar to satsumas, (TV: The Christmas Invasion) they were also frequently given on Christmas.
According to a dream version of Santa Claus, tangerines were his signature gift. The Twelfth Doctor, on the other hand, claimed that, "no-one likes the tangerines". When Santa and his elves came to the rescue on the arctic base, the first thing to come in was a tangerine. After the Twelfth Doctor and Clara Oswald resumed travelling with each other, a tangerine was left on Clara's windowsill. (TV: Last Christmas)