Unusual event in diffuse nebula is not so exciting (15)
I believe the answer is:
unexceptionable
'exciting' is the definition.
Both the answer and definition are adjectives. Perhaps they are linked in a way I don't understand?
'unusual event in diffuse nebula is not' is the wordplay.
I cannot quite understand how this works, but
'not' could be 'o' (I've seen this in other clues) and 'o' is found in the answer.
'in' is present in the answer.
This explanation may well be incorrect...
'so' is the link.
Can you help me to learn more?
(Another definition for unexceptionable that I've seen is " entirely satisfactory".)