Check energy consumption during fire (7)
I believe the answer is:
setback
'check' is the definition.
(I've seen this before)
'energy consumption during fire' is the wordplay.
'energy' becomes 'e' (physics symbol as in E=mc2).
'consumption' becomes 'tb' (consumption is a name for TB or tuberculosis).
'during' is an insertion indicator.
'fire' becomes 'sack' (dismiss someone from their job).
'e'+'tb'='etb'
'etb' put inside 'sack' is 'SETBACK'.
(Other definitions for setback that I've seen before include "Problem" , "disappointment" , "Reverse" , "Check" , "Hindrance to progress" .)