The digger has a name for it (7)
I believe the answer is:
mineral
'the digger' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'a name for it' is the wordplay.
'a name' becomes 'al'.
'for' says to put letters next to each other (I've seen this in other clues).
'it' becomes 'miner' (I can't explain this - if you can you should give a lot more credence to this answer).
'al' put after 'miner' is 'MINERAL'.
'has' is the link.
Can you help me to learn more?
(Other definitions for mineral that I've seen before include "Zinc or magnesium, say" , "Gypsum or magnesia, say" , "Substance that is (usually) inorganic" , "What drink is available in ground" , "Substance needed for health; ore" .)