Some rock and lead, say, have melted and tamely liquefied (5,5)
I believe the answer is:
heavy metal
'some rock' is the definition.
(heavy metal is a rock genre)
'lead say have melted and tamely liquefied' is the wordplay.
I cannot really see how this works, but
an anagram of 'have' is 'heav' which is within the answer.
an anagram of 'tamely' is 'ymetal' which is within the answer.
This accounts for all the letters.
This may be the basis of clue (or it may be nonsense).
'and' acts as a link.
Can you help me to learn more?
(Other definitions for heavy metal that I've seen before include "Typically, lead" , "Loud form of rock" , "hard rock" , "Loud rock music" , "Iron" .)