Golfer PA upset in childish game (8)
I believe the answer is:
leapfrog
'childish game' is the definition.
'leapfrog' can be an answer for 'game' (leapfrog is a kind of game). I am not certain of the 'childish' bit.
'golfer pa upset' is the wordplay.
'upset' indicates an anagram.
'golfer'+'pa'='golferpa'
'golferpa' with letters rearranged gives 'LEAPFROG'.
'in' is the link.
Can you help me to learn more?
(Other definitions for leapfrog that I've seen before include "Vaulting game" , "Children's game of jumping over each other" , "Children's game in which one jumps over the other alternately" , "Child's game of jumping over competitors" , "Game in which one child jumps over another" .)