Small vegetable is shiny (5)
I believe the answer is:
sleek
'shiny' is the definition.
(thesaurus)
'small vegetable' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'vegetable' becomes 'leek' (leek is a kind of vegetable).
's'+'leek'='SLEEK'
'is' is the link.
(Other definitions for sleek that I've seen before include "Smooth - well-fed" , "Pleasingly smooth" , "Aerodynamic, streamlined" , "Looking prosperous" , "Excessively well-groomed" .)