Open coal fires I left to go out (8)
I believe the answer is:
alfresco
'open' is the definition.
(I've seen this before)
'coal fires i left to go out' is the wordplay.
'left' is a deletion indicator.
'to go out' is an anagram indicator.
'coal'+'fires'='coalfires'
'coalfires' with 'i' removed is 'coalfres'.
'coalfres' is an anagram of 'ALFRESCO'.
(Other definitions for alfresco that I've seen before include "where it's cool" , "Outside" , "Open-air" , "Out of doors" , "exposed to the fresh air" .)