Footwear that's smooth and too short (7)
I believe the answer is:
sandals
'footwear' is the definition.
(I've seen this before)
'smooth and too short' is the wordplay.
'smooth' becomes 'sand' (sanding is a kind of smoothing).
'and' becomes 'also'.
'too short' means to remove the last letter.
'also' with its last letter taken away is 'als'.
'sand'+'als'='SANDALS'
'that's' acts as a link.
(Other definitions for sandals that I've seen before include "Open footwear" , "Soles strapped to the feet" , "Light open shoes" .)