Spooner's low bit is over the top (3,4)

I believe the answer is:

too much

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'over the top' is the definition.

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

(Other definitions for too much that I've seen before include "Beyond endurance" , "Excessive amount - far out!" , "Excess, more than is needed" , "See 17" , "Excessive, overwhelming" .)

I've seen this clue in The Guardian.

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