Part of the fireplace to renew (7)
I believe the answer is:
replace
'renew' is the definition.
(replacing is a kind of renewing)
'part of the fireplace to' is the wordplay.
'part of' says the answer is hidden in the clue.
'REPLACE' can be found hidden inside 'fireplace to'.
(Other definitions for replace that I've seen before include "Substitute for (someone)" , "Substitute, supersede" , "Put back where you found it" , "Put back or substitute" , "Provide a substitute for" .)