The most common and most likely answer to this crossword clue is the 3 plus 7 letter word GIG ECONOMY
I've seen this crossword clue in The Guardian
G
I
G
E
C
O
N
O
M
Y
Buddy explains!
The straight part
We know that "system that favours fat cats" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case system that favours fat cats = gig economy.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.