Very small can with yellow front (4)
I believe the answer is:
tiny
'very small' is the definition.
(I've seen this before)
'can with yellow front' is the wordplay.
'can' becomes 'tin' (both are metal containers).
'with' is a charade indicator (letters next to each other).
'front' suggests taking the first letters.
The first letter of 'yellow' is 'y'.
'tin'+'y'='TINY'
(Other definitions for tiny that I've seen before include "- - Tim (Dickens)" , "Quite insignificant" , "Extremely small" , "Diminutive; small" , "Minuscule" .)