Nut on car shattered (5)
I believe the answer is:
acorn
'nut' is the definition.
(I've seen this in another clue)
'on car shattered' is the wordplay.
'shattered' indicates an anagram.
'on'+'car'='oncar'
'oncar' is an anagram of 'ACORN'.
(Other definitions for acorn that I've seen before include "Potential oak" , "old computer?" , "oak's fruit" , "fruit in a cup" , "Nut of oak tree" .)