Unrestrained harangue involving a member of parliament (7)
I believe the answer is:
rampant
'unrestrained' is the definition.
(I've seen this in another clue)
'harangue involving a member of parliament' is the wordplay.
'harangue' becomes 'rant' (synonyms).
'involving' indicates putting letters inside.
'member of parliament' becomes 'MP' (abbreviation).
'a'+'mp'='amp'
'rant' going around 'amp' is 'RAMPANT'.
(Other definitions for rampant that I've seen before include "Flourishing excessively as disease may be" , "Out of control" , "running wild" , "On the rampage" , "Uncontrolled" .)