Person who furtively steals footwear (7)
I believe the answer is:
sneaker
'footwear' is the definition.
(sneaker is a kind of footwear)
'person who furtively steals' is the wordplay.
I cannot quite see how this works, but
'person' could be 'sneak' (sneak is a kind of person) and 'sneak' is present in the answer.
The remaining letters 'er' 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 sneaker that I've seen before include "Casual shoe" , "American trainer" , "Trainer (shoe)" , "Canvas shoe" , "Soft shoe" .)