Popular set that holds messages for you (5)
I believe the answer is:
inbox
'holds messages for you' is the definition.
I know nothing about this answer so I cannot tell whether this works.
'popular set' is the wordplay.
'popular' becomes 'in' ('in' can mean trendy).
'set' becomes 'box' (I can't explain this - if you can you should believe this answer much more).
'in'+'box'='INBOX'
'that' is the link.
Can you help me to learn more?
(Other definitions for inbox that I've seen before include "Folder receiving emails" , "file" , "Email folder" .)