French collaborator from SAS keeping down (8)

I believe the answer is:

saunders

I'm a little stuck... Click here to teach me more about this clue!

'french collaborator' is the definition.
I know nothing about this answer so I can't judge whether this works.

'sas keeping down' is the wordplay.
'keeping' means one lot of letters goes inside another.
'down' becomes 'under' (I've seen this before).
'sas' placed around 'under' is 'SAUNDERS'.

'from' acts as a link.

Can you help me to learn more?

I've seen this clue in The Sun.

Want a hint initially instead of a full solution? Install my app