Some share Greta's sorrow (6)
I believe the answer is:
regret
'sorrow' is the definition.
(I know that sorrow can be written as regret)
'some share greta's' is the wordplay.
'some' indicates a hidden word (some of the parts of the word are used).
'REGRET' can be found hidden inside 'share greta'.
(Other definitions for regret that I've seen before include "Feel sad or disappointed about" , "Mourn" , "Compunction" , "Sorrow for something done" , "Rue, repine" .)