Lots of folk run in casual footwear (7)
I believe the answer is:
throngs
'lots' is the definition.
(I have seen 'Lots of people' mean 'throngs' so perhaps 'lots' could also mean 'throngs')
'folk run in casual footwear' is the wordplay.
I cannot quite understand how this works, but
'run' could be 'r' (cricket abbreviation) and 'r' is found within the answer.
'footwear' could be 'thongs' (I've seen this before) and 'thongs' is located in the leftover letters.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
'of' acts as a link.
Can you help me to learn more?
(Other definitions for throngs that I've seen before include "Crowds" , "Lots of people" .)