Carelessly train, for example, with something so heavy. (7)
I believe the answer is:
granite
'heavy' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.
'carelessly train for example with something' is the wordplay.
I cannot really see how this works, but
an anagram of 'train' is 'ranit' which is located in the answer.
The remaining letters 'ge' 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).
'so' is the link.
Can you help me to learn more?
(Other definitions for granite that I've seen before include "Get rain (anag) - rock" , "Hard granular rock" , "Very hard type of rock" , "Tearing (anag.)" , "Tangier (anag.)" .)