Unrestrained, a politician during tirade (7)
I believe the answer is:
rampant
'unrestrained' is the definition.
(I've seen this before)
'a politician during tirade' is the wordplay.
'politician' becomes 'MP' (Member of Parliament).
'during' is an insertion indicator.
'tirade' becomes 'rant' (both can mean an angry outburst).
'a'+'mp'='amp'
'amp' going into 'rant' is 'RAMPANT'.
(Other definitions for rampant that I've seen before include "Flourishing excessively as disease may be" , "Uncontrolled" , "Showing unchecked growth" , "Mantrap (anag) - unrestrained" , "Out of control" .)