The most common and most likely answer to this crossword clue is the 9 letter word IMPULSION
I
M
P
U
L
S
I
O
N
Buddy explains!

The straight part
We know that "Force" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case force = impulsion.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 IMPULSION mean?
IMPULSION noun- The act of impelling or driving onward, or the state of being impelled; the sudden or momentary agency of a body in motion on another body; also, the impelling force, or impulse.
- Influence acting unexpectedly or temporarily on the mind; sudden motive or influence; impulse.