Smooth son in clubs (5)
I believe the answer is:
irons
'clubs' is the definition.
(I know that iron is a type of clubs)
'smooth son' is the wordplay.
'smooth' becomes 'iron' (to smooth down with an iron).
'son' becomes 's' (genealogical abbreviation for son).
'iron'+'s'='IRONS'
'in' acts as a link.
(Other definitions for irons that I've seen before include "Metal leg shackles" , "Imposers of restrictions" , "cuffs" , "Golf-clubs with metal heads" , "Smooths, presses" .)