Wrench restricting one part of body or another (4-3)
I believe the answer is:
rear-end
'wrench restricting' is the definition.
I can't tell whether this definition defines the answer.
'one part of body or another' is the wordplay.
'one part of body' becomes 'rear' ('rear' is part of 'body').
'or another' becomes 'end' (I can't justify this - if you can you should believe this answer much more).
'rear'+'end'='REAR-END'
(Other definitions for rear-end that I've seen before include "Crash into another vehicle from behind (US)" , "hit a vehicle" , "Crash into back of another vehicle" .)