A cereal's covering in, say, maple syrup (7)

I believe the answer is:

treacle

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

(Other definitions for treacle that I've seen before include "Dark viscous 11" , "Syrup, molasses" , "Something cloyingly sweet" , "Syrup-like substance" , "Sweet, sticky stuff" .)

I've seen this clue in The Telegraph.

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