The most common and most likely answer to this crossword clue is the 4 plus 4 letter word WIND FARM
I've seen this crossword clue in The Guardian
W
I
N
D
F
A
R
M
More clues leading to the result WIND FARM
- Concentration of turbines turn a long way, miles
- Spooner’s to come across kind-hearted energy supplier
- Discover heat to exchange leads in energy plant
- Independent female stops near turbines
- Western firm and new supplier of energy
- Feel hot when exchanging caps in generator
- Take what beans produce and cultivate for green energy source
- Exchanging introductions, discover friendly energy supplier
- Find fault in friendly source of power
Buddy explains!

The straight part
We know that "source of power" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case source of power = wind farm.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.