Failure to remember men lost in Far East (7)
I believe the answer is:
amnesia
'failure to remember' is the definition.
I can't judge whether this definition defines the answer.
'men lost in far east' is the wordplay.
'lost' is an anagram indicator.
'in' is an insertion indicator.
'far east' becomes 'asia' (the Far East is part of Asia).
'men' anagrammed gives 'mne'.
'mne' inserted inside 'asia' is 'AMNESIA'.
Can you help me to learn more?
(Other definitions for amnesia that I've seen before include "Main sea (anag.)" , "Pathological forgetfulness" , "Memory-loss" , "Mental condition" , "Seaman I found in state of memory loss" .)