Tirade about a member of parliament that’s unrestrained (7)
I believe the answer is:
rampant
'unrestrained' is the definition.
(thesaurus)
'tirade about a member of parliament' is the wordplay.
'tirade' becomes 'rant' (I've seen this before).
'about' means one lot of letters goes inside another.
'member of parliament' becomes 'mp' (I've seen this in other clues).
'a'+'mp'='amp'
'rant' going around 'amp' is 'RAMPANT'.
'that's' acts as a link.
(Other definitions for rampant that I've seen before include "Spreading unchecked" , "Out of control" , "Unchecked (and violent?)" , "Mantrap (anag) - unrestrained" , "Flourishing excessively as disease may be" .)