Miner's tailless dog (6)
I believe the answer is:
collie
'dog' is the definition.
(collie is a kind of dog)
'miner's tailless' is the wordplay.
'miner' becomes 'collier' (collier is a kind of miner).
'tailless' means to remove the last letter.
'collier' with its final letter removed is 'COLLIE'.
(Other definitions for collie that I've seen before include "Sheepdog with long pointed muzzle" , "Breed of dog" , "Silky-coated sheepdog" , "Long-haired sheepdog" , "Popular sheepdog like Lassie" .)