Exceptional transport commandered by queens turned up (8)

I believe the answer is:

singular

'exceptional' is the definition.
(I've seen this before)

I can't explain the rest of the clue.

(Other definitions for singular that I've seen before include "number" , "Unusual, striking, or unique" , "One of a kind" , "Remarkable - unique" , "Referring to one thing" .)

I've seen this clue in The Guardian.

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Exceptional transport comman­dered by queens turned up (8)

Exceptional transport commandered by queens turned up (8)