Fellow outside prison about to get mechanical restriction (7)
I believe the answer is:
manacle
'mechanical restriction' is the definition.
'fellow outside prison about' is the wordplay.
'fellow' becomes 'male' (I've seen this before**).
'outside' indicates putting letters inside.
'prison' becomes 'can' (the can is American slang for prison).
'about' is a reversal indicator.
'can' in reverse letter order is 'nac'.
'male' going around 'nac' is 'MANACLE'.
'to get' acts as a link.
(Other definitions for manacle that I've seen before include "Fetter" , "Hand/ankle restraint" , "Curb" , "Shackle on the wrist" , "Handcuff" .)