Clue: Small mammal contracted disease, unfortunately (6)
Answer: DASSIE
Explanation: Definition: Small mammal
Anagram of DISEAS[E] – a small rat-like mammal, also known as the Hyrax. Rather obscure, perhaps, but the clueing is clear, and there are surprisingly few words that fit the pattern _A_S_E: perhaps Paul didn't fancy clueing HASSLE, LASSIE or even FALSIE..