The most common and most likely answer to this crossword clue is the 8 letter word VOLTAGES
I've seen this crossword clue in The Daily Telegraph
V
O
L
T
A
G
E
S
Buddy explains!
The straight part
We know that "Forces" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case forces = voltages.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.
What does VOLTAGES mean?
VOLTAGES noun- The difference in electrostatic potential between two points in space, especially between live and neutral conductors or the earth.