Spell 'vase' after bit of tuition (4)
I believe the answer is:
turn
'spell' is the definition.
('turn' can be a synonym of 'spell')
'vase after bit of tuition' is the wordplay.
'vase' becomes 'urn' (urn is a kind of vase).
'after' is a charade indicator (letters next to each other).
'bit of' says to take the initial letters.
The first letter of 'tuition' is 't'.
'urn' put after 't' is 'TURN'.
(Other definitions for turn that I've seen before include "Go - go round in circles - go off" , "Move in a new direction" , "revolutionary act" , "Shock - move - change course" , "Go; spin (cricket)" .)