A source of problems in poor golfer's game (8)
I believe the answer is:
leapfrog
'game' is the definition.
(leapfrog is a kind of game)
'a source of problems in poor golfer's' is the wordplay.
'source of' suggests taking the first letters.
'in' is an insertion indicator.
'poor' is an anagram indicator.
The first letter of 'problems' is 'p'.
'a'+'p'='ap'
'golfer' is an anagram of 'lefrog'.
'ap' put within 'lefrog' is 'LEAPFROG'.
(Other definitions for leapfrog that I've seen before include "Game in which one child jumps over another" , "Playground game" , "Overtake in position" , "Advance by jumping over the opposition" , "Game in which players vault over each other" .)