Kiln's fuel ran low every so often when they made a large fire (7)
I believe the answer is:
inferno
'a large fire' is the definition.
(I've seen this before)
'kiln's fuel ran low every so often' is the wordplay.
'every so often' indicates alternate letters.
'kilns'+'fuel'+'ran'+'low'='kilnsfuelranlow'
The alternating letters of 'kilnsfuelranlow' are 'INFERNO'.
'when they made' is the link.
This may not be right. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for inferno that I've seen before include "Fierce fire" , "Dante's Hell" , "(Hellish) blaze" , "Hellish conflagration" , "Nine Circles here" .)