Mild-mannered chap emptied latrine (6)
I believe the answer is:
gentle
'mild-mannered' is the definition.
(I've seen this before)
'chap emptied latrine' is the wordplay.
'chap' becomes 'gent' (I've seen this in other clues).
'emptied' suggests removing the centre.
'latrine' with its middle removed is 'le'.
'gent'+'le'='GENTLE'
(Other definitions for gentle that I've seen before include "Mild and benign" , "Soft and mild, quiet and soothing" , "Jane Eyre's kind person with a book? -- eternal greed (anag)" , "Mild; a maggot" , "amiable" .)