Not Stevenson's better half (4)

I believe the answer is:

hyde

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'half' is the definition.
Both the definition and answer are singular nouns.
Perhaps they are linked in a way I don't understand?

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for hyde that I've seen before include "Jekyll's alter ego" , "Green space in London" , "and 21 Across: Green area in London" , "The evil personality (see 12)" , "doctor turned into during work" .)

I've seen this clue in The Globe and Mail.

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