Dogmatist's piece about good love (5)
I believe the answer is:
bigot
'dogmatist's' is the definition.
(I've seen this before)
'piece about good love' is the wordplay.
'piece' becomes 'bit' (bit is a kind of piece).
'about' is an insertion indicator.
'good' becomes 'g' (abbreviation).
'love' becomes 'o' (love means zero in tennis).
'g'+'o'='go'
'bit' enclosing 'go' is 'BIGOT'.
(Other definitions for bigot that I've seen before include "Intolerantly prejudiced person" , "Dogmatist" , "One is prejudiced and intolerant" , "sectarian" , "Someone intolerant of opinions of others" .)