Reserve following very bad habit (4)
I believe the answer is:
vice
'bad habit' is the definition.
(thesaurus)
'reserve following very' is the wordplay.
'reserve' becomes 'ice' (I've seen this before).
'following' means one lot of letters go next to another.
'very' becomes 'v' (abbreviation).
'ice' put after 'v' is 'VICE'.
(Other definitions for vice that I've seen before include "Gripping tool - bad habit" , "Is the gripping tool evil?" , "person to stand in for skipper" , "Gripper - depravity" , "may have a powerful grip" .)