The most common and most likely answer to this crossword clue is the 10 letter word CAPITALIST
I've seen this crossword clue in The Guardian
C
A
P
I
T
A
L
I
S
T
More clues leading to the result CAPITALIST
- Beat it with very famous investor
- Better use of computers — a tip for businessman?
- Profit-seeker’s hat, the thing in front of a catalogue
- Supporter of an economic system that is disastrous
- What can be said of Trump or one like Trump?
- Investor being excellent is beginning to thrive
- IST tycoon
- Investor first to support Tokyo, for example
- Before the conclusion of Brexit I can be found in Berlin and Paris, possibly, as profiteer
- Somewhere like London is spot ultimately for businessperson?
Buddy explains!

The straight part
We know that "Supporter of an economic system" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case supporter of an economic system = capitalist.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 CAPITALIST mean?
CAPITALIST noun- A person who is a supporter of capitalism.
- The owner of a considerable amount of capital; a wealthy person.
- Of, or pertaining to, capitalism.
- Supporting or endorsing capitalism.