The most common and most likely answer to this crossword clue is the 6 letter word IMPACT
I've seen this crossword clue in The Guardian
I
M
P
A
C
T
More clues leading to the result IMPACT
- Legislator blocking current law's effect
- Influence thing done by little devil
- Consequences of one initially minor agreement
- Something performed by troublemaker for powerful effect
- Effect of one parliamentary bill introduced by member
- Influence the process of old-fashioned graft?
- Force top Frenchman to return in middle of site
- Independent memberis a hit
- Significance of devil’s work?
- Main road heading north jammed, according to report – a crash
Buddy explains!

The straight part
We know that "Significance" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case significance = impact.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 IMPACT mean?
IMPACT noun- The striking of one body against another; collision.
- The force or energy of a collision of two objects.
- A forced impinging.
- A significant or strong influence; an effect.
- To collide or strike, the act of impinging.
- To compress; to compact; to press into something or pack together.
- To influence; to affect; to have an impact on.
- To stamp or impress onto something.