Shudder in great remorse (6)
I believe the answer is:
tremor
'shudder' is the definition.
(synonyms)
'in great remorse' is the wordplay.
'in' indicates a hidden word.
'TREMOR' can be found hidden inside 'great remorse'.
(Other definitions for tremor that I've seen before include "Quavering" , "Small earthquake" , "A little agitation" , "A small shake, perhaps of earth ( 6)" , "Involuntary quiver" .)