Leave boring part for sectarian (5)
I believe the answer is:
bigot
'sectarian' is the definition.
(I've seen this before)
'leave boring part' is the wordplay.
'leave' becomes 'go'.
'boring' indicates putting letters inside (some letters must 'bore' a hole into other letters).
'part' becomes 'bit' (both mean a piece of something).
'go' going inside 'bit' is 'BIGOT'.
'for' acts as a link.
(Other definitions for bigot that I've seen before include "Intolerant type" , "One is prejudiced and intolerant" , "Fanatic" , "Racist or sexist?" , "Intolerantly prejudiced person" .)