This leg broken through dexterity (7)
I believe the answer is:
sleight
'dexterity' is the definition.
(I know that dexterity can be written as sleight)
'this leg broken' is the wordplay.
'broken' indicates anagramming the letters.
'this'+'leg'='thisleg'
'thisleg' with letters rearranged gives 'SLEIGHT'.
'through' acts as a link.
(Other definitions for sleight that I've seen before include "craft" , "It's deceiving to the eye" , "Manual dexterity" , "Hits leg (anag) - cunning" , "distraction?" .)