Thick stick as weapon (6)
I believe the answer is:
cudgel
'thick stick as weapon' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for cudgel that I've seen before include "Heavy stick or club as a weapon" , "(Strike with a) heavy stick" , "Stout stick used as a weapon" , "Heavy staff, club" , "brain" .)