The most common and most likely answer to this crossword clue is the 7 letter word HOPPING
I've seen this crossword clue in The Sunday Telegraph
H
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More clues leading to the result HOPPING
Buddy explains!

The straight part
We know that "Gathering fruit from some climbers/how mad can one be?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case gathering fruit from some climbers/how mad can one be? = hopping.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 HOPPING mean?
HOPPING noun- Hop picking, the practice of picking hops; for Londoners a holiday period working in the hop gardens of Kent.
- The addition of hops during the production of beer as a flavouring agent
- To jump a short distance.
- To jump on one foot.
- To be in state of energetic activity.
- To suddenly take a mode of transportation that one does not drive oneself, often surreptitiously.
- To jump onto, or over
- (usually in combination) To move frequently from one place or situation to another similar one.
- To walk lame; to limp.
- To dance.
- To impregnate with hops, especially to add hops as a flavouring agent during the production of beer
- To gather hops.
- The act of one who, or that which, hops; a jumping, frisking, or dancing.
- A shift from one energy-state to another by an electron in an atom.
- Of a location, crowded with people.