Presumption about Republican's indiscretion (10)
I believe the answer is:
imprudence
'indiscretion' is the definition.
(I've seen this before)
'presumption about republican's' is the wordplay.
'presumption' becomes 'impudence' (both can mean impertinent behaviour).
'about' indicates putting letters inside.
'republican' becomes 'r' (abbreviation).
'impudence' going around 'r' is 'IMPRUDENCE'.
(Other definitions for imprudence that I've seen before include "An unwise act" , "lack of caution" , "Injudiciousness" , "Thoughtlessness" , "foolishness" .)