Endless, asinine rubbish about Instagram symbol (8)
I believe the answer is:
insignia
'symbol' is the definition.
(insignia is a kind of symbol)
'endless asinine rubbish about' is the wordplay.
'endless asinine rubbish' becomes 'insigni' (I can't justify this - if you can you should give a lot more credence to this answer).
'about' becomes 'a' (abbreviation in Chambers).
'insigni'+'a'='INSIGNIA'
'instagram' acts as a link.
I am not very happy about this link. It may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for insignia that I've seen before include "Badges of office" , "arms" , "Stars and stripes, say" , "Badge of membership" , "marks" .)