Smooth golf club (4)
I believe the answer is:
iron
I believe this is a double definition.
'smooth' is the first definition.
(I've seen this before)
'golf club' is the second definition.
(I've seen this in another clue)
(Other definitions for iron that I've seen before include "Very robust" , "inflexible > club" , "What's used to make pitch" , "rations in emergency?" , "Club; element" .)