Poor miner with nothing but sheep (6)
I believe the answer is:
merino
'sheep' is the definition.
(merino sheep is a kind of sheep)
'poor miner with nothing' is the wordplay.
'poor' indicates an anagram.
'with nothing' becomes 'o' (I've seen this in other clues).
'miner' is an anagram of 'merin'.
'merin'+'o'='MERINO'
'but' acts as a link.
(Other definitions for merino that I've seen before include "Long-haired sheep" , "No rime for this sheep" , "Type of sheep" , "Fine-woolled sheep" , "Sheep from Spain with a heavy quality fleece" .)