The most common and most likely answer to this crossword clue is the 8 letter word FOOTFALL
I've seen this crossword clue in The Guardian
F
O
O
T
F
A
L
L
More clues leading to the result FOOTFALL
- Pay decrease for a number of people entering shop
- Number of customers in time to pay for trip
- Settle for drop in customer numbers
- Commercial patronage of sport lacking breadth but therein gaining following
- Step flat out to intercept 31
- Number of people entering Foreign Office with book before autumn in the U.S.
Buddy explains!

The straight part
We know that "Number of customers in time" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case number of customers in time = footfall.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 FOOTFALL mean?
FOOTFALL noun- The sound made by a footstep.
- Foot (pedestrian) traffic.