Device for connecting plug, suitable in the place of missing lead (7)

I believe the answer is:

adaptor

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But I can't explain it at all! Could you help me understand?

(Other definitions for adaptor that I've seen before include "Device for connecting multiple plugs (O, not E)" , "Kind of electric plug" , "Electrical device" , "Connector for differing plug types" , "It enables fit" .)

I've seen this clue in The Telegraph.

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