Concedes the tailless swallow looks very odd (6)

I believe the answer is:

allows

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'concedes' is the definition.
('allow' can be a synonym of 'concede')

I don't understand the rest of the clue.

(Other definitions for allows that I've seen before include "Sallow (anag.)" , "Grants leave" , "Permits, lets" , "Permits to do something" , "Tolerates" .)

I've seen this clue in the Evening Standard.

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