Memory loss in a very big area worried men (7)
I believe the answer is:
amnesia
'memory loss' is the definition.
(synonyms)
'in a very big area worried men' is the wordplay.
'in' indicates putting letters inside.
'a very big area' becomes 'asia' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'worried' is an anagram indicator (worry can mean to interfere with or disturb).
'men' anagrammed gives 'mne'.
'asia' placed around 'mne' is 'AMNESIA'.
Can you help me to learn more?
(Other definitions for amnesia that I've seen before include "Am I sane? (anag)" , "Clinical loss of memory" , "Defect in memory" , "Inability to remember" , "Pathological forgetfulness" .)