The most common and most likely answer to this crossword clue is the 8 letter word MOMENTUM
M
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M
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M
More clues leading to the result MOMENTUM
- Male with some guts shows force
- Political group’s instant sign of hesitation
- Impetus in a short time followed by hesitation
- Impetus bringing hesitation after a little while
- Instant character rejection that has helped scupper Labour?
- Silent about foreboding at the launch of this political movement
- Force doctor and staff to join corporation
- Left wing group takes little time getting males on corporation
- Short time with hesitation giving impetus
- Energy shown by second Greek character turning up
Buddy explains!

The straight part
We know that "left-wing group" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case left-wing group = momentum.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 MOMENTUM mean?
MOMENTUM noun- Of a body in motion: the tendency of a body to maintain its inertial motion; the product of its mass and velocity.
- The impetus, either of a body in motion, or of an idea or course of events; a moment.