A swinging club (4)
I believe the answer is:
iron
This might be a double definition.
'a swinging' is the first definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.
'club' is the second definition.
(iron is a kind of club)
Can you help me to learn more?
(Other definitions for iron that I've seen before include "resolve" , "Heavy metal that rusts easily" , "sort of club" , "Smooth; element" , "Very robust" .)