Horror-struck scallywag has turned to bottle (6)
I believe the answer is:
aghast
'horror-struck' is the definition.
(I've seen this before)
'scallywag has turned to bottle' is the wordplay.
'to bottle' indicates a hidden word (I've seen 'bottles' mean this (bottling is a kind of containing)).
'AGHAST' is hidden in the letters of 'scallywag has turned'.
(Other definitions for aghast that I've seen before include "in awe" , "Horrified, appalled" , "struck with fear" , "Very unhappy" , "Stupefied with horrer" .)