The most common and most likely answer to this crossword clue is the 10 letter word STEPLADDER
I've seen this crossword clue in The Times
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More clues leading to the result STEPLADDER
- Walk, run, climb on it
- It helps to climb, walk and run
- Heading for peak, chap departs wearing guide's climbing equipment
- Rung up repeatedly on this, when given run on stage
- Turning, cats maybe run: one could climb this?
- Temporary flight in summer carrying large pets up
- Help for climber very inclined to lose heart, left hanging over the summer
- It is inclined to raise one’s standing
- Something in tool shed maybe has left little darlings upset — snake
- It could get you to plastered drywall’s top when rebuilding
Buddy explains!

The straight part
We know that "climb on it" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case climb on it = stepladder.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 STEPLADDER mean?
STEPLADDER noun- A ladder with steps or treads instead of rungs that is hinged in the middle to form an inverted V, with stays to keep the two halves at a fixed angle.
- The player over whom another player marks to take a spectacular mark.