The most common and most likely answer to this crossword clue is the 9 letter word COLLATION
I've seen this crossword clue in Financial Times
C
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The straight part
We know that "Assembling/a light meal" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case assembling/a light meal = collation.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 COLLATION mean?
COLLATION noun- Bringing together.
- Discussion, light meal.
- The presentation of a clergyman to a benefice by a bishop, who has it in his own gift.
- (inheritance) The blending together of property so as to achieve equal division, mainly in the case of inheritance.
- (inheritance) An heir's right to combine the whole heritable and movable estates of the deceased into one mass, sharing it equally with others who are of the same degree of kindred.
- The act of conferring or bestowing.
- Presentation to a benefice.
- To partake of a collation, or light meal.