Bear has no time to be smooth (4)
I believe the answer is:
sand
'smooth' is the definition.
(sanding is a kind of smoothing)
'bear has no time' is the wordplay.
'bear' becomes 'stand' ('stand' can be a synonym of 'bear').
'has no' suggests deleting specific letters.
'time' becomes 't'.
'stand' with 't' removed is 'SAND'.
'to be' is the link.
(Other definitions for sand that I've seen before include "Shore grain" , "Rub down (for painting)" , "Parts of beach" , "lover of Chopin" , "Desert material" .)