It’s easily bought online on Kindle primarily (1-4)
I believe the answer is:
e-book
'it's' is the definition.
I know nothing about this answer so I cannot judge whether it can be defined by this definition.
'easily bought online on kindle primarily' is the wordplay.
'primarily' suggests taking the first letters.
The first letters of 'easily bought online on kindle' is 'E-BOOK'.
Can you help me to learn more?
(Other definitions for e-book that I've seen before include "Volume in electronic form" , "Electronic reading material" , "Downloaded volume" , "Non-paper publication" , "Literature from the internet" .)