The most common and most likely answer to this crossword clue is the 8 letter word PLETHORA
I've seen this crossword clue in Financial Times
P
L
E
T
H
O
R
A
More clues leading to the result PLETHORA
- No shortage of fabulous help with rota
- “Heap” and “lot” could be about right for this?
- Other pal made up excess
- Request that God divides wealth
- Request to admit Thunderer is too much!
- Through prayer, God provides abundance
- God inspired by prayer a lot
- Flood defence breached by Norse god
- Moving to her lap leads to excess
- God is into prayer a lot
Buddy explains!

The straight part
We know that "Large number" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case large number = plethora.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 PLETHORA mean?
PLETHORA noun- (usually followed by of) An excessive amount or number; an abundance.
- An excess of red blood cells or bodily humours.