Rodent not lacking stomach eating a sort of light pastry (3-2-4)
I believe the answer is:
vol-au-vent
'pastry' is the definition.
(vol-au-vent is a kind of pastry)
'rodent not lacking stomach eating a sort of light' is the wordplay.
'rodent' becomes 'vole' (vole is a kind of rodent).
'lacking stomach' says to hollow out the word (remove centre letters) (the word's guts are removed).
'eating' is an insertion indicator.
'sort of light' becomes 'uv' (short for ultraviolet light).
'not' with its middle removed is 'nt'.
'vole'+'nt'='volent'
'a'+'uv'='auv'
'volent' going around 'auv' is 'VOL-AU-VENT'.
(Other definitions for vol-au-vent that I've seen before include "Small puff pastry case with savoury filling" , "Light, filled pastry shell" , "Small puff pastry with fish or meat" , "Puff-pastry savoury" .)