Measure what one eats a bit at a time (8)

'measure what one eats a bit at a time' is the definition.
I can't judge whether this definition defines the answer.

'measure what one eats a' is the wordplay.
'measure' becomes 'inch' (inch is a unit of length).
'what' becomes 'mel' (I can't justify this - if you can you should believe this answer much more).
'one eats' means one lot of letters goes inside another.
'mel' placed around 'a' is 'meal'.
'inch'+'meal'='INCHMEAL'

Can you help me to learn more?