Is coal even a source of energy? (3)
I believe the answer is:
sol
'a source of energy?' is the definition.
I can't tell whether this defines the answer.
'is coal even' is the wordplay.
'even' indicates alternate letters (letters in even-numbered positions are used).
'is'+'coal'='iscoal'
The alternating letters of 'iscoal' are 'SOL'.
Can you help me to learn more?
(Other definitions for sol that I've seen before include "Roman counterpart of Helios" , "The sun in 12 Across" , "The Sun (or Campbell?)" , "Musical note" , "Note, old french coin" .)