Leather

Leather was a material made by tanning animal skins. (TV: The Coach with the Dragon Tattoo)

After the death of Lucie Miller, the Eighth Doctor added more leather to his ensemble, specifically a navy blue leather jacket. (AUDIO: Fugitives) This carried through to the end of that incarnation. (TV: The Night of the Doctor) The War Doctor wore a different style of leather jacket, making it suitable for battle. (TV: The Name of the Doctor, The Night of the Doctor, The Day of the Doctor) His ninth incarnation wore a similar style as part of his main wardrobe. (TV: Rose et al.)

Candy DuFries always carried a battered leather satchel full of watercolours. (PROSE: Eternity Weeps)

The symbiotic Fliis planned to take over humans on Earth in the 20th century. They disguised themselves as leather jackets to trick people into wearing and bonding with them. (COMIC: Fashion Victims)

Ram Singh suggested that a male skin-peeling dragon make Coach Dawson's skin into leather, "make a chair or something", in order to preserve his mate. (TV: The Coach with the Dragon Tattoo)

In the 24th century, hidehogs were genetically engineered animals used to produce leather. (PROSE: To the Slaughter)

The skins of ghouties could be made into leather. They looked like a cross between a donkey and a three toed sloth, and were found on Thanaxos. (PROSE: The Mary-Sue Extrusion)

The Slabs were made of leather. (TV: Smith and Jones)