Illuminating sign made lone appearance in hours of darkness (4,5)
I believe the answer is:
neon light
'illuminating sign' is the definition.
I don't know anything about this answer so I cannot judge whether it can be defined by this definition.
'lone appearance in hours of darkness' is the wordplay.
I cannot really see how this works, but
an anagram of 'lone' is 'eonl' which is present in the answer.
'hours' could be 'night' (I have seen 'Hours of darkness' mean 'night' so perhaps 'hours' could also mean 'night') and 'night' is found within the leftover letters.
No letters remain.
This explanation may well be incorrect...
'made' acts as a link.
Can you help me to learn more?
(Other definitions for neon light that I've seen before include "Illumination used for advertising" , "Advertising sign, perhaps" , "Source of illumination" , "What may shine" , "Type of illumination" .)