Creep undermining women's golf club (5)
I believe the answer is:
wedge
'golf club' is the definition.
(type of golf club)
'creep undermining women's' is the wordplay.
'creep' becomes 'edge' (I've seen this before).
'undermining' says to put letters next to each other.
'women' becomes 'w' (standard abbreviation).
'edge' put after 'w' is 'WEDGE'.
(Other definitions for wedge that I've seen before include "Tapering piece" , "Splitting device" , "V-sign" , "Significant amount of money (informal)" , "Chock" .)