Incompetent type, one blowing something out of proportion, ultimately (7)

I believe the answer is:

bungler

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'incompetent' is the definition.
(I know that bungler is a type of incompetent)

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for bungler that I've seen before include "One prone to error" , "Clumsy incompetent" , "Clumsy executant" , "Someone prone to getting it wrong" .)

I've seen this clue in The Times.

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