Sad people row — yours truly's upset initially (8)

'sad people' is the definition.
(a sad person might be called a misery)

'row yours truly's upset initially' is the wordplay.
'row' becomes 'series' (both can mean a sequence of things).
'yours truly's' becomes 'I'm' (I'm).
'upset' shows that the letters should be reversed in order.
'initially' says to put letters next to each other.
'im' reversed gives 'mi'.
'series' after 'mi' is 'MISERIES'.