The most common and most likely answer to this crossword clue is the 10 letter word PATRONISES
I've seen this crossword clue in The Guardian
P
A
T
R
O
N
I
S
E
S
Buddy explains!

The straight part
We know that "Supports" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case supports = patronises.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 PATRONISES mean?
PATRONISES verb- To act as a patron of; to defend, protect, or support.
- To make oneself a customer of a business, especially a regular customer.
- To assume a tone of unjustified superiority toward; to talk down to, to treat condescendingly.
- To blame, to reproach.