Heavy metal intro from Metallica interrupts match interval (4,4)
I believe the answer is:
cast iron
'heavy metal' is the definition.
(I've seen this in another clue)
'intro from metallica interrupts match interval' is the wordplay.
I cannot quite see how this works, but
an anagram of 'intro' is 'tiron' which is within the answer.
The remaining letters 'cas' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for cast iron that I've seen before include "Firm and unchangeable" , "Brittle alloy" , "safe" , "Unarguable; alloy" , "Solid, robust" .)