The most common and most likely answer to this crossword clue is the 8 letter word CADDYING
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More clues leading to the result CADDYING
Buddy explains!

The straight part
We know that "working as a golfer's assistant" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case working as a golfer's assistant = caddying.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does CADDYING mean?
CADDYING verb- To serve as a golf caddie.
- To serve as a caddy, carrying golf clubs etc.