Measure reduction in customer levels (8)
I believe the answer is:
footfall
'reduction in customer levels' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.
'measure' is the wordplay.
I cannot really understand how this works, but
'measure' could be 'foot' (foot is a kind of measure) and 'foot' is located in the answer.
The remaining letters 'fall' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for footfall that I've seen before include "Sound of step" , "Customers" , "Sound of someone walking" , "Commercial patronage" .)