ET (say) crashed into sides of cone reflector (4-3)
I believe the answer is:
cats-eye
'reflector' is the definition.
(reflective device on a road)
'et say crashed into sides of cone' is the wordplay.
'crashed' is an anagram indicator.
'into' indicates putting letters inside.
'sides of' suggests removing the centre (only the letters on the sides remain).
'cone' with its middle taken out is 'ce'.
'et'+'say'='etsay'
'etsay' is an anagram of 'atsey'.
'atsey' put within 'ce' is 'CATS-EYE'.
(Other definitions for cats-eye that I've seen before include "Gem; road reflector" , "Small glass device in a road surface" , "One of those in the middle of the road" , "Semi-precious stone; road reflector" , "Reflectors in a road surface (3'1,3)" .)