Soil is black, say, except initially round the edge (7)

'soil' is the definition.
(I know that soil can be written as begrime)

'is black say except initially round the edge' is the wordplay.
I cannot really understand how this works, but
'is' could be 'be' and 'be' is located in the answer.
'black' could be 'grim' (synonyms) and 'grim' is found in the answer.
A single letter 'e' remains which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?