Mild oath for Saint Babe (6)

I believe the answer is:

struth

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

'mild oath' is the definition.
I don't know anything about this answer so I cannot judge whether this works.

'saint babe' is the wordplay.
'saint' becomes 'st'.
'babe' becomes 'ruth' (I've seen this before).
'st'+'ruth'='STRUTH'

'for' is the link.

Can you help me to learn more?

I've seen this clue in the Sydney Morning Herald.

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