Working below Irish golf club (4)
I believe the answer is:
iron
'golf club' is the definition.
(I've seen this before)
'working below irish' is the wordplay.
'working' becomes 'on'.
'below' means one lot of letters go next to another.
'irish' becomes 'ir' (abbreviation).
'on' after 'ir' is 'IRON'.
(Other definitions for iron that I've seen before include "Hard metal" , "stern" , "great strength" , "sports club" , "Smooth - press - club" .)