Educated girl eating a yoghurt-based side dish (5)
I believe the answer is:
raita
'yoghurt-based side dish' is the definition.
(Indian side dish)
'educated girl eating a' is the wordplay.
'educated girl' becomes 'rita' (in the play and film Educating Rita).
'eating' indicates putting letters inside.
'rita' placed around 'a' is 'RAITA'.
(Other definitions for raita that I've seen before include "Indian side-dish of yogurt and cucumber" , "Indian side dish of yogurt and chopped cucumber" , "Indian food good as side-dish" , "Cucumber and mint Indian dip" , "Dishy thing" .)