Free English parliamentarian trapped in extension (6)
I believe the answer is:
exempt
'free' is the definition.
(exempt can mean to free or release)
'english parliamentarian trapped in extension' is the wordplay.
'english' becomes 'e' (abbreviation).
'parliamentarian' becomes 'MP' (Member of Parliament).
'trapped in' indicates putting letters inside.
'extension' becomes 'ext' (abbreviation, as in a telephone extension).
'e'+'mp'='emp'
'emp' placed within 'ext' is 'EXEMPT'.
(Other definitions for exempt that I've seen before include "Excused - let off" , "Free from, eg, tax" , "Not subject to a law" , "Free from liability. excused" , "Immune - absolve" .)