Dwarf planet absorbing odd bits of meteor mass — astronaut's opening tinned food? (4,6)

'tinned food?' is the definition.
(plum tomatoes are often sold in tins)

'dwarf planet absorbing odd bits of meteor mass astronaut's opening' is the wordplay.
'dwarf planet' becomes 'pluto' (Pluto is a dwarf planet).
'absorbing' is an insertion indicator.
'odd bits of' indicates alternate letters.
'opening' says to take the initial letters.
The first letters of 'mass astronauts' is 'ma'.
The alternating letters of 'meteor' are 'mto'.
'mto'+'ma'='mtoma'
'pluto' placed around 'mtoma' is 'PLUM TOMATO'.