Pitman's dog needing run (7)
I believe the answer is:
collier
'pitman's' is the definition.
(synonyms)
'dog needing run' is the wordplay.
I cannot quite see how this works, but
'dog' could be 'collie' (collie is a kind of dog) and 'collie' is found in the answer.
'run' could be 'r' (cricket abbreviation) and 'r' is found within the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for collier that I've seen before include "Miner; coal ship" , "Worker down under" , "Pitman" , "Geordie Jack, commonly" , "unable to avoid contact with mine" .)