This appeared at the end of the Eighties (6)
I believe the answer is:
ninety
'end of the eighties' is the definition.
Both the answer and definition are adjectives. Perhaps they are linked in a way I don't understand?
'this appeared at the' is the wordplay.
I cannot really see how this works, but
'at' could be 'in' and 'in' is found within the answer.
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is present in the answer.
The remaining letters 'ney' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for ninety that I've seen before include "6 x 3 x 5" , "Fourscore and ten" , "XC (in ancient Rome)" , "Cardinal" , "''Oh, the craic was ... in the Isle of Man'' (The Dubliners)" .)