It helps to forget different men in a large part of the world (7)
I believe the answer is:
amnesia
'it helps to forget' is the definition.
(amnesia is memory loss)
'different men in a large part of the world' is the wordplay.
'different' is an anagram indicator.
'in' means one lot of letters goes inside another.
'a large part of the world' becomes 'Asia' (Asia is a continent).
'men' with letters rearranged gives 'mne'.
'mne' going within 'asia' is 'AMNESIA'.
(Other definitions for amnesia that I've seen before include "Inability to remember" , "Is a name (anag.)" , "Seaman I find suffering from memory loss" , "Am I sane? (anag)" , "Clinical state of forgetfulness" .)