Grossly immoral conduct can obviously be gripping (4)
I believe the answer is:
vice
'grossly immoral conduct' is the definition.
The definition and answer can be both acts as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for vice that I've seen before include "venality?" , "Wrong" , "Prefix for deputy to, say, chairman" , "Gripper - in place of - immorality" , "Prefix meaning acting as deputy" .)