Ex UN Chief is a non-aligned national (5)
I believe the answer is:
annan
'ex un chief' is the definition.
I don't know anything about this answer so I cannot tell whether it can be defined by this definition.
'a non-aligned national' is the wordplay.
'a' becomes 'an'.
'non aligned national' becomes 'nan' (this might be a standard abbreviation which I don't know about).
'an'+'nan'='ANNAN'
'is' acts as a link.
Can you help me to learn more?
(Other definitions for annan that I've seen before include "UN Secretary-General, 1997-2006" , "Ban predecessor" , "Kofi -, UN Secretary-General" .)