It’s sensible to have the animal, a lion, tied up (8)

I believe the answer is:

rational

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'it's sensible' is the definition.
(associated in meaning)

I cannot understand how the remainder of the clue works.

(Other definitions for rational that I've seen before include "In accordance with logic" , "Clear-headed" , "Endowed with reason" , "Sane and logical" , "Conforming to reason" .)

I've seen this clue in the Evening Standard.

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