Is around, perhaps, but it disappeared ages ago (8)
I believe the answer is:
dinosaur
'it disappeared ages ago' is the definition.
The definition suggests a singular noun which matches the answer.
'is around perhaps' is the wordplay.
'perhaps' is an anagram indicator.
'is'+'around'='isaround'
'isaround' with letters rearranged gives 'DINOSAUR'.
'but' acts as a link.
Can you help me to learn more?
(Other definitions for dinosaur that I've seen before include "Extinct monster like Barney, children's TV pal" , "Prehistoric monster from Jurassic era" , "Settle under canvas" , "Extinct beast" , "Eg, triceratops" .)