It stores images showing popular pair of beastly males (9)
I believe the answer is:
'it stores images' is the definition.
(Instagram is a photo-based social network)
'popular pair of beastly males' is the wordplay.
I cannot quite understand how this works, but
'popular' could be 'in' ('in' can mean trendy) and 'in' is found in the answer.
This explanation may well be incorrect...
'showing' is the link.
I've seen this clue in The Guardian.
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