Golfer takes two pairs of socks in case he gets such a hole (2,3)
I believe the answer is:
in one
'golfer takes two pairs of socks' is the definition.
I know nothing about this answer so I can't judge whether it can be defined by this definition.
'in case he gets such a hole' is the wordplay.
'case he' becomes 'ne' (I am not sure about this - if you are sure you should believe this answer much more).
'gets' means one lot of letters goes inside another (gets can mean captures or absorbs).
'such a hole' becomes 'O'.
'in'+'ne'='inne'
'inne' going around 'o' is 'IN ONE'.
Can you help me to learn more?
(Other definitions for in one that I've seen before include "united" , "A hole . . . . . is a singular golf score" , "Combined" , "As a single unit" .)