Lack of enthusiasm showing in an issue editor cancelled (9)
I believe the answer is:
inanition
'lack' is the definition.
(I have seen 'lack of enthusiasm' mean 'inanition' so perhaps 'lack' could also mean 'inanition')
'of enthusiasm showing in an issue editor cancelled' is the wordplay.
'of enthusiasm' becomes 'nani' (I can't justify this - if you can you should believe this answer much more).
'showing in' means one lot of letters goes inside another.
'an issue' becomes 'edition' (edition is a kind of issue).
'editor' becomes 'ed' (abbreviation).
'cancelled' indicates named letters should be taken away.
'edition' with 'ed' taken out is 'ition'.
'nani' put inside 'ition' is 'INANITION'.
Can you help me to learn more?
(Other definitions for inanition that I've seen before include "Lack of vigour" , "being exhausted" , "Lassitude" , "Exhaustion" , "lack of enthusiasm" .)