Shocked seeing part of bag has torn (6)
I believe the answer is:
aghast
'shocked' is the definition.
('aghast' can be a synonym of 'shocked')
'part of bag has torn' is the wordplay.
'part of' indicates a hidden word.
'AGHAST' can be found hidden inside 'bag has torn'.
'seeing' acts as a link.
(Other definitions for aghast that I've seen before include "Stunned" , "Filled with fear or horror" , "Horror-stricken, filled with consternation" , "Confounded" , "'Horrified, shocked (6)'" .)