Valiant attempt to repress one's initial prejudice (7)
I believe the answer is:
bigotry
'initial prejudice' is the definition.
'bigotry' can be an answer for 'prejudice' (bigotry means prejudice or discrimination). I am not sure about the 'initial' bit.
'valiant attempt to repress one's' is the wordplay.
'valiant' becomes 'big' (big can mean brave).
'attempt' becomes 'try' (synonyms).
'to' means one lot of letters go next to another (I've seen this in other clues).
'repress one' becomes 'o' (I can't explain this - if you can you should believe this answer much more).
'try' put after 'o' is 'otry'.
'big'+'otry'='BIGOTRY'
Can you help me to learn more?
(Other definitions for bigotry that I've seen before include "Intolerance, prejudice on grounds of religion" , "Blind zeal" , "Intolerant prejudice" , "Stubborn prejudice" .)