Legs in motion, making one run (6)
I believe the answer is:
single
'one run' is the definition.
(type of run in cricket)
'legs in motion' is the wordplay.
'motion' is an anagram indicator.
'legs'+'in'='legsin'
'legsin' anagrammed gives 'SINGLE'.
'making' acts as a link.
(Other definitions for single that I've seen before include "Unattached" , "Like bachelor" , "A hit for one run in cricket" , "Concentrating on only one aim" , "Individual - unmarried" .)