Sorry to have to dash back, breathless (3)

I believe the answer is:

sad

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'sorry' is the definition.
(similar in meaning)

I cannot understand how the rest of the clue works.

(Other definitions for sad that I've seen before include "Dejected" , "'Unhappy, sorry (3)'" , "Melancholy or pitiful" , "Regrettable" , "Dismal" .)

I've seen this clue in the Evening Standard.

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