Only bit of footwear? (4)
I believe the answer is:
sole
I believe this is a double definition.
'only' is the first definition.
(synonyms)
'bit of footwear?' is the second definition.
('sole' is part of 'footwear')
(Other definitions for sole that I've seen before include "European flatfish" , "piece of leather" , "One and only; part of foot" , "Underside of the foot" , "Flatfish; exclusive" .)