Murphy, maybe, could have dug one up (5)
I believe the answer is:
tuber
'murphy' is the definition.
Although both the answer and definition are singular nouns, I can't understand how one could define the other.
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for tuber that I've seen before include "Thickened fleshy root" , "Fleshy root, vegetable say" , "Root eg of potato" , "Root of potato etc" , "One goes underground" .)