Refreshment essential for golfer on links course (4,8)
I believe the answer is:
club sandwich
'refreshment' is the definition.
'essential for golfer on links course' is the wordplay.
'essential for golfer' becomes 'club' (a golf club is an essential item for a golfer).
'on' says to put letters next to each other.
'links course' becomes 'sandwich' (Sandwich is home to a links golf course).
'club'+'sandwich'='CLUB SANDWICH'
(Other definitions for club sandwich that I've seen before include "extra large snack" , "Three or more slices of bread with fillings" , "Double-decker" , "Three-layer snack" .)