Dog right for a miner (7)
I believe the answer is:
collier
'a miner' is the definition.
(collier is a kind of miner)
'dog right for' is the wordplay.
'dog' becomes 'collie' (collie is a kind of dog).
'right for' becomes 'r' (I've seen this in other clues).
'collie'+'r'='COLLIER'
(Other definitions for collier that I've seen before include "Worker down under" , "Pitman" , "He works in a coal mine" , "Geordie Jack, commonly" , "British coal-miner" .)