Broken bone somehow compressing extremely tough joint (2,3,5)
I believe the answer is:
on the blink
'broken' is the definition.
(something on the blink is not working properly)
'bone somehow compressing extremely tough joint' is the wordplay.
'somehow' is an anagram indicator.
'compressing' is an insertion indicator (inserted letters get compressed between others).
'extremely' suggests removing the centre (letters on the extremes of the word are used).
'joint' becomes 'link' (joints link things together).
'tough' with its middle taken out is 'th'.
'bone' with letters rearranged gives 'oneb'.
'oneb' enclosing 'th' is 'ontheb'.
'ontheb'+'link'='ON THE BLINK'
(Other definitions for on the blink that I've seen before include "out of order" , "getting poor reception" , "Not working properly" .)