Left helpless: sad trend needs change (8)
I believe the answer is:
stranded
'left helpless' is the definition.
(I've seen this in another clue)
'sad trend needs change' is the wordplay.
'needs change' indicates anagramming the letters (I've seen 'needs changing' mean this (I've seen this in other clues)).
'sad'+'trend'='sadtrend'
'sadtrend' is an anagram of 'STRANDED'.
(Other definitions for stranded that I've seen before include "Like rope" , "Left aground on a shore" , "Left high and dry, deserted" , "Left in helpless condition" , "Left behind" .)