Remove lid of box, then take half for domesticated animals (4)

I believe the answer is:

oxen

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'animals' is the definition.
(I've seen this before)

I don't understand how the remainder of the clue works.

(Other definitions for oxen that I've seen before include "Beasts of burden or domestic cattle" , "Domesticated bovine draft animals" , "Domesticated bovines" , "strong animals" , "Domestic bovines" .)

I've seen this clue in The Irish Times.

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