The ability to persevere with a hard substance, I say (6)
I believe the answer is:
mettle
'the ability' is the definition.
The answer and definition can be both human attributes as well as being singular nouns.
Perhaps there's an association between them I don't understand?
'persevere with a hard substance i say' is the wordplay.
I cannot quite see how this works, but
'substance' could be 'tl' (Tl is an example) and 'tl' is located in the answer.
'i' could be 'me' and 'me' is located in the answer.
The remaining letters 'te' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
'to' is the link.
Can you help me to learn more?
(Other definitions for mettle that I've seen before include "Temperament; courage" , "Strength of character, courage" , "Bravery" , "The courage to carry on" , "Pluck" .)