It’s great to upset this hidebound fellow! (5)
I believe the answer is:
bigot
'this hidebound fellow' is the definition.
'bigot' can be an answer for 'hidebound' (thesaurus). I'm not certain of the rest of the definition.
'it's great to upset' is the wordplay.
'it's great' becomes 'big' ('big' can be a synonym of 'great').
'upset' says the letters should be written backwards.
'to' written backwards gives 'ot'.
'big'+'ot'='BIGOT'
Can you help me to learn more?
(Other definitions for bigot that I've seen before include "One is prejudiced and intolerant" , "Someone intolerant of opinions of others" , "Fanatic" , "Deeply prejudiced and intolerant person" , "Intolerantly prejudiced person" .)