Intercede when a friend's about to die, possibly? (7)
I believe the answer is:
mediate
'intercede' is the definition.
(synonyms)
'a friend's about to die possibly?' is the wordplay.
'a friend' becomes 'mate' (mate is a kind of friend).
'about' means one lot of letters goes inside another.
'possibly?' is an anagram indicator (I've seen 'possibly' mean this).
'die' anagrammed gives 'edi'.
'mate' enclosing 'edi' is 'MEDIATE'.
'when' acts as a link.
(Other definitions for mediate that I've seen before include "Intercede" , "Help settle a dispute" , "Act as middle man" , "Conciliate" , "To referee" .)