The most common and most likely answer to this crossword clue is the 7 letter word PROJECT
I've seen this crossword clue in The Guardian
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More clues leading to the result PROJECT
- Stand out, as low-cost housing
- School research task needs to stand out
- Undertaking to stick out
- Planned programme in favour of Jung’s initial shock treatment
- Stick out for proposal
- Plan for fast plane, including maximum speed
- Stick out for a planned undertaking
- Estimate for maximum possible speed in plane
- Launch scheme
- Throw out a proposed scheme
Buddy explains!

The straight part
We know that "Campaign" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case campaign = project.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 PROJECT mean?
PROJECT noun- A planned endeavor, usually with a specific goal and accomplished in several steps or stages.
- (usually in the plural) An urban low-income housing building.
- An idle scheme; an impracticable design.
- A raw recruit who the team hopes will improve greatly with coaching; a long shot diamond in the rough
- A projectile.
- A projection.
- The place from which a thing projects.
- To extend beyond a surface.
- To cast (an image or shadow) upon a surface; to throw or cast forward; to shoot forth.
- To extend (a protrusion or appendage) outward.
- To make plans for; to forecast.
- To present (oneself), to convey a certain impression, usually in a good way.
- To assume qualities or mindsets in others based on one's own personality.
- To change the projection (or coordinate system) of spatial data with another projection.
- To draw straight lines from a fixed point through every point of any body or figure, and let these fall upon a surface so as to form the points of a new figure.