A person I have forgotten sadly is close to death (3,4,2,3,5)
I believe the answer is:
one foot in the grave
'a person i have forgotten sadly is close to death' is the definition.
I know nothing about this answer so I cannot judge whether this works.
'i have forgotten sadly is close to death' is the wordplay.
'sadly' indicates anagramming the letters.
'is close to' is a charade indicator (letters next to each other).
'death' becomes 'one' (I can't justify this - if you can you should believe this answer much more).
'i'+'have'+'forgotten'='ihaveforgotten'
'ihaveforgotten' is an anagram of 'footinthegrave'.
'footinthegrave' after 'one' is 'ONE FOOT IN THE GRAVE'.
Can you help me to learn more?
(Other definitions for one foot in the grave that I've seen before include "TV show" , "Near death; TV sitcom (3,4,2,3,5)" , "a forerunner to Six Feet Under?" .)