Shortest routine? (7)
If this is the answer, I'm afraid I cannot explain it.
Can you help me to learn more?
(Another definition for onestep that I've seen is " (Very short?) ballroom dance".)
'shortest routine?' is the definition.
The answer and definition can be both acts as well as being singular nouns.
Maybe there's an association between them I don't understand?
This is all the clue.
Can you help me to learn more?
(Other definitions for one-step that I've seen before include "Foxtrot's precursor" , "Vigorous dance" , "Kind of foxtrot" , "Style of foxtrot" , "(Very short?) ballroom dance" .)