Former PM repeatedly to hinder adult play (5,7)
I believe the answer is:
major barbara
'play' is the definition.
(I've seen this before)
'former pm repeatedly to hinder adult' is the wordplay.
'former pm' becomes 'major' (I've seen this before).
'repeatedly' says to double the letters.
'to hinder' becomes 'bar' (I've seen this in another clue).
'adult' becomes 'a' (abbreviation).
'bar' duplicated is 'barbar'.
'major'+'barbar'+'a'='MAJOR BARBARA'
(Other definitions for major barbara that I've seen before include "G.B. Shaw play" , "GBS Salvation Army heroine" .)