In Germany with little sister, occupied by ordinary division of cells (7)

'division of cells' is the definition.
'mitosis' can be an answer for 'division' (type of cell division). I'm not sure about the 'of cells' bit.

'in germany with little sister occupied by ordinary' is the wordplay.
I cannot quite see how this works, but
'sister' could be 'sis' (synonyms) and 'sis' is found in the answer.
'ordinary' could be 'o' (abbreviation eg in O-Level, Ordinary Level) and 'o' is found within the answer.
The remaining letters 'mit' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?