Stone and nickel in fireplace (7)
I believe the answer is:
granite
'stone' is the definition.
(I've seen this before)
'nickel in fireplace' is the wordplay.
'nickel' becomes 'ni' (Ni is the chemical symbol for nickel).
'in' means one lot of letters goes inside another.
'fireplace' becomes 'grate' (I've seen this before).
'ni' placed inside 'grate' is 'GRANITE'.
'and' acts as a link.
(Other definitions for granite that I've seen before include "Very hard type of rock" , "Coarse-grained igneous rock" , "Tearing (anag.)" , "Hard granular rock" , "Resilience; stone" .)