Russian politician still to admit large crime (7)
I believe the answer is:
yeltsin
'russian politician' is the definition.
(Boris Yeltsin)
'still to admit large crime' is the wordplay.
'still' becomes 'yet' ('yet' can be a synonym of 'still').
'to admit' is an insertion indicator.
'large' becomes 'l'.
'crime' becomes 'sin'.
'yet' placed around 'l' is 'yelt'.
'yelt'+'sin'='YELTSIN'
(Other definitions for yeltsin that I've seen before include "Boris --, former Russian politician" , "Nineteen ninety's Russian president" , "Boris . . . . . . Russian chief" , "Russian leader" , "Russian statesman" .)