John almost upended George (5)
I believe the answer is:
eliot
'george' is the definition.
(I've seen this before)
'john almost upended' is the wordplay.
'john' becomes 'toilet' (synonyms).
'almost' means to remove the last letter (almost the whole word is kept).
'upended' shows that the letters should be reversed in order (in a down clue, letters go up).
'toilet' with its final letter removed is 'toile'.
'toile' reversed gives 'ELIOT'.
(Other definitions for eliot that I've seen before include "George - - (novelist)" , "T.S. or George?" , "See 14" , "British poet, d. 1965" , "Author of Adam Bede, d.1880" .)