Framework used in the training of climbers (7)

I believe the answer is:

trellis

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'framework' is the definition.
(I know that trellis is a type of fretwork)

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for trellis that I've seen before include "Train for plants" , "Frame for creepers" , "Support for creepers" , "Garden framework for climbers" , "Garden lattice" .)

I've seen this clue in The Irish News.

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