Crossword Genius

In conclusion, layabout primarily swings the lead (6)

Ross

I believe the answer is:

lastly

'in conclusion' is the definition.
(synonyms)

I can't explain the rest of the clue.

(Other definitions for lastly that I've seen before include "In conclusion" , "In the end" , "Finally, to conclude with" .)

I've seen this clue in The Guardian.
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