Copied it totally, but only a part is the same again (5)
I believe the answer is:
ditto
'is the same again' is the definition.
(I've seen this before)
'copied it totally but only a part' is the wordplay.
'only a part' says the answer is hidden in the clue (I've seen 'only a part of' mean this).
'DITTO' is hidden within 'copied it totally but'.
(Other definitions for ditto that I've seen before include "Mark used to indicate the word above it should be repeated" , "Same again, indicated by two dots" , "Likewise" , "As per previous" , "Notation meaning the same again" .)