Irish speaker’s turn of phrase in heavy metal (7)
I believe the answer is:
iridium
'heavy metal' is the definition.
(I've seen this before)
'irish speaker's turn of phrase' is the wordplay.
I cannot really see how this works, but
'irish' could be 'ir' (abbreviation) and 'ir' is found in the answer.
'turn' could be 'u' (a 'U-turn' is a kind of turn) and 'u' is found within the answer.
This explanation may well be incorrect...
'in' is the link.
(Other definitions for iridium that I've seen before include "Element, symbol Ir" , "number 77" , "Hard metal element, Ir" , "Hard metallic element" , "Heavy brittle metallic element of the platinum group" .)