The most common and most likely answer to this crossword clue is the 10 letter word MISERICORD
I've seen this crossword clue in The Guardian
M
I
S
E
R
I
C
O
R
D
Buddy explains!

The straight part
We know that "Support found in church" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case support found in church = misericord.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 MISERICORD mean?
MISERICORD noun- Relaxation of monastic rules.
- The room in a monastery for monks granted such relaxation.
- A ledge, sometimes ornately carved, attached to a folding church seat to provide support for a person standing for long periods; a subsellium.
- A medieval dagger, used for the mercy stroke to a wounded foe.