Reminders being married, a little upset (5)
I believe the answer is:
memos
'reminders' is the definition.
(short for memoranda)
'married a little upset' is the wordplay.
'married' becomes 'm'.
'a little' becomes 'some' (I've seen this before).
'upset' shows that the letters should be reversed in order.
'some' backwards is 'emos'.
'm'+'emos'='MEMOS'
'being' is the link.
(Other definitions for memos that I've seen before include "Records" , "Short notes" , "Written notes" , "Inter-office notes" .)