Confines or rather restricts spy boss (5)
I believe the answer is:
ambit
'confines' is the definition.
(ambit means the confines or scope of something)
'rather restricts spy boss' is the wordplay.
'rather' becomes 'a bit' ('a bit' can mean rather or to some extent).
'restricts' is an insertion indicator.
'spy boss' becomes 'M' (M is the head of MI6 in the James Bond series).
'abit' enclosing 'm' is 'AMBIT'.
'or' is the link.
(Other definitions for ambit that I've seen before include "Circuit, compass" , "Range, scope" , "Scope or circuit" , "Compass, scope" , "Circumference" .)