Broken leg reduced activity (6)
I believe the answer is:
bustle
'activity' is the definition.
(I've seen this before)
'broken leg reduced' is the wordplay.
'broken' becomes 'bust' (bust can mean broken).
'reduced' means to remove the last letter.
'leg' with its last letter removed is 'le'.
'bust'+'le'='BUSTLE'
(Other definitions for bustle that I've seen before include "Frame under a dress" , "Fuss about part of woman's dress of old" , "Busy oneself noisily about the former feature of women's dress" , "Hurried and noisy activity" , "Excited activity of subtle sort" .)