"Hound has rare distinguishing mark on it" (6)
The 4th letter is 'G' so I'm thinking 'beagle' but I'm not sure how the rest of the clue points to that - an anagram of beagle is glebae which is 'The fleshy, spore-bearing inner mass of a puffball' but does that count as a distinguishing mark?
Help would be much appreciated! :)