PM, nasty about Labour's leader, getting victory (7)
I believe the answer is:
baldwin
'pm' is the definition.
(I have seen 'Former PM' mean 'baldwin' so perhaps 'pm' could also mean 'baldwin')
'nasty about labour's leader getting victory' is the wordplay.
'nasty' becomes 'bad' (I've seen this in another clue).
'about' indicates putting letters inside.
'labour's leader' becomes 'l'.
'getting' says to put letters next to each other.
'victory' becomes 'win' (a win is a victory).
'bad' placed around 'l' is 'bald'.
'bald'+'win'='BALDWIN'
(Other definitions for baldwin that I've seen before include "Prime minister" , "British PM three times between WWI and WWII" , "British statesman" , "Former PM" , "Medieval monarch - black American writer - British premier" .)