Shelled nuts beside vase making quite a change! (1-4)
I believe the answer is:
u-turn
'quite a change' is the definition.
(a dramatic change in opinion or policy)
'shelled nuts beside vase' is the wordplay.
'shelled' indicates the central letters (the outer letters or shell are removed).
'beside' is a charade indicator (letters next to each other) (I've seen this in other clues).
'vase' becomes 'urn' (urn is a kind of vase).
The central letters of 'nuts' are 'ut'.
'ut'+'urn'='U-TURN'
'making' acts as a link.
(Other definitions for u-turn that I've seen before include "drastic change" , "Complete reverse of car on public road" , "A complete reverse of direction" , "180deg change of direction" , "180 degrees change of direction" .)