One, following destruction of Reims, is close to death (2,8)
I believe the answer is:
in extremis
'close to death' is the definition.
I can't tell whether this defines the answer.
'one following destruction of reims' is the wordplay.
'one' becomes 'i' (roman numeral).
'following' becomes 'next' (synonyms).
'destruction of' indicates anagramming the letters.
'reims' is an anagram of 'remis'.
'i'+'next'+'remis'='IN EXTREMIS'
'is' acts as a link.
Can you help me to learn more?
(Other definitions for in extremis that I've seen before include "as last resort" , "feeling desperation" , "Facing death" , "dying" , "at a desperate point" .)