Stitch up celebrity cut by Republican leader (5)
I believe the answer is:
frame
'stitch up' is the definition.
(I've seen this before)
'celebrity cut by republican leader' is the wordplay.
'celebrity' becomes 'fame' ('fame' can be a synonym of 'celebrity').
'cut by' indicates putting letters inside.
'leader' indicates taking the first letters.
The initial letter of 'republican' is 'r'.
'fame' placed around 'r' is 'FRAME'.
(Other definitions for frame that I've seen before include "physique" , "One game of snooker" , "Stitch up!" , "Potter's half-hour or so" , "mould" .)