Old prejudice, ultimately, gets the Magi moving (6)
I believe the answer is:
ageism
'old prejudice' is the definition.
'ageism' can be an answer for 'prejudice' (prejudice against older people). I am unsure of the 'old' bit.
'ultimately gets the magi moving' is the wordplay.
'ultimately' suggests the final letters.
'moving' indicates an anagram (letters are moved around).
The final letters of 'gets the' are 'se'.
'se'+'magi'='semagi'
'semagi' anagrammed gives 'AGEISM'.
Can you help me to learn more?
(Other definitions for ageism that I've seen before include "Prejudice on grounds of advanced years" , "discriminating against the elderly?" , "Discrimination on the basis of longevity" , "Discrimination e.g. against old people" , "Prejudice on grounds of age" .)