Emit, when exonerated (3,3)

I believe the answer is:

let off

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'emit' is the definition.
The definition and answer can be both to do with communicating as well as being verbs in their base form.
Maybe there's a link between them I don't understand?

I don't understand the rest of the clue.

Can you help me to learn more?

(Other definitions for let off that I've seen before include "Not punished at all" , "Set free without charge" , "Release by exploding - pardon" , "Spare" , "Allow to go free; discharge" .)

I've seen this clue in the Evening Standard.

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