Loss of memory (7)
I believe the answer is:
'loss of memory' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for amnesia that I've seen before include "Asia men with memory loss (7)" , "Pathological forgetfulness" , "Seaman I found in state of memory loss" , "As a mine (anag)" , "memory problem" .)