Think about donkey's daughter losing last lover (4,4)

I believe the answer is:

mull over

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

'donkey's daughter losing last lover' is the definition.
I can't judge whether this definition defines the answer.

'think about' is the wordplay.
'think' becomes 'mull' (mulling is a kind of thinking).
'about' becomes 'over' (both can mean around).
'mull'+'over'='MULL OVER'

Can you help me to learn more?

(Other definitions for mull over that I've seen before include "Consider" , "Ruminate, ponder" .)

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

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