The most common and most likely answer to this crossword clue is the 11 letter word BITTERSWEET
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More clues leading to the result BITTERSWEET
Buddy explains!

The straight part
We know that "Climber" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case climber = bittersweet.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 BITTERSWEET mean?
BITTERSWEET noun- Solanum dulcamara.
- Bittersweetness.
- A vine, of the genus Celastrus, having small orange fruit that open to reveal red seeds.
- A variety of apple with a bittersweet taste.
- Any variety of clam in the family Glycymerididae
- A pinkish-orange color. Any color in between scarlet and orange.
- Both bitter and sweet.
- Expressing contrasting emotions of pain and pleasure.
- Of bittersweet color.