Mime 'Eros Undone' or learn by heart (8)
I believe the answer is:
memorise
'learn by heart' is the definition.
(I've seen this before)
'mime eros undone' is the wordplay.
'undone' is an anagram indicator (the original order is undone).
'mime'+'eros'='mimeeros'
'mimeeros' anagrammed gives 'MEMORISE'.
'or' is the link.
(Other definitions for memorise that I've seen before include "Learn by heart" , "Commit information to the mind" .)