American girl designing shoes as foot-protectors (8)
I believe the answer is:
galoshes
'foot-protectors' is the definition.
(galoshes are worn over shoes)
'american girl designing shoes' is the wordplay.
'american girl' becomes 'gal' (US term for a girl).
'designing' indicates anagramming the letters.
'shoes' anagrammed gives 'oshes'.
'gal'+'oshes'='GALOSHES'
'as' acts as a link.
(Other definitions for galoshes that I've seen before include "footwear" , "Go hassle to get overshoes" , "Overshoes usually made of rubber" , "Waterproof overshoes" .)