Paper working to limit Republican club (4)
I believe the answer is:
iron
'club' is the definition.
(iron is a kind of club)
'paper working to limit republican' is the wordplay.
'paper' becomes 'i' (UK newspaper).
'working' becomes 'on'.
'to limit' means one lot of letters goes inside another.
'republican' becomes 'r' (abbreviation).
'i'+'on'='ion'
'ion' going around 'r' is 'IRON'.
(Other definitions for iron that I've seen before include "Heavy metal that rusts easily" , "Strong metal; golf club" , "Former dividing line across Europe" , "Main component of steel" , "Main part of steel" .)