Has once pinched the backside of Little Ted? (5)
I believe the answer is:
heath
'ted?' is the definition.
(Ted Heath, UK prime minister 1970-74)
'has once pinched the backside of little' is the wordplay.
'has once' becomes 'hath' (historical form of 'has').
'pinched' means one lot of letters goes inside another.
'the backside of' indicates one should take the final letters.
The last letter of 'little' is 'e'.
'hath' going around 'e' is 'HEATH'.
(Other definitions for heath that I've seen before include "Area of common unproductive land" , "Ex-Tory PM" , "Open uncultivated land" , "See 16" , "Shrubby area of open country" .)