Peg out to follow rotter, golfer’s attendant (6)
I believe the answer is:
caddie
'golfer's attendant' is the definition.
(I've seen this before)
'peg out to follow rotter' is the wordplay.
'peg out' becomes 'die'.
'to follow' means one lot of letters go next to another.
'rotter' becomes 'cad' (I've seen this before).
'die' after 'cad' is 'CADDIE'.
(Other definitions for caddie that I've seen before include "Golfer's attendant" , "Assistant to carry the golf clubs" , "Golfer's assistant on course" , "Golfing assistant" , "A golfer's assistant (6)" .)