Conservative in struggle for grip (4)
I believe the answer is:
vice
'for grip' is the definition.
(I've seen this before)
'conservative in struggle' is the wordplay.
'conservative' becomes 'C' (UK political abbreviation).
'in' means one lot of letters goes inside another.
'struggle' becomes 'vie' (to vie is to struggle or contend with).
'c' put within 'vie' is 'VICE'.
(Other definitions for vice that I've seen before include "person to stand in for skipper" , "Tool with gripping jaws" , "Gripper - sin" , "Gripper -- fault" , "Gripping tool - bad habit" .)