Broken coal ovens — they can produce lots of smoke! (9)
I believe the answer is:
volcanoes
'they can produce lots of smoke' is the definition.
(smoke may come from a volcano)
'broken coal ovens' is the wordplay.
'broken' is an anagram indicator.
'coal'+'ovens'='coalovens'
'coalovens' is an anagram of 'VOLCANOES'.
(Other definitions for volcanoes that I've seen before include "sources of warm flows" , "Lava spewers" , "Erupting fissures in the earth's crust" , "Fissures in the earth's surface that emit lava" .)