The most common and most likely answer to this crossword clue is the 10 letter word ALLEGIANCE
I've seen this crossword clue in The Daily Telegraph
A
L
L
E
G
I
A
N
C
E
More clues leading to the result ALLEGIANCE
- Commitment for one in marriage
- Loyalty for example accepted by coalition
- Loyalty is required, say, in a union
- Fidelity, for example, is required in marriage
- Union accepting banks in Greece raised duty
- Loyalty, say, found in union
- Support for Nigella, ace when cooking
- Loyalty is required, say, in union
- Loyalty, for example, in combine
- Loyalty, say, within marriage
Buddy explains!
The straight part
We know that "Support" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case support = allegiance.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 ALLEGIANCE mean?
ALLEGIANCE noun- Loyalty to some cause, nation or ruler.