Mull over strange case after maiden disappears (8)
I believe the answer is:
ruminate
'mull over' is the definition.
(synonyms)
'strange case after maiden disappears' is the wordplay.
I cannot really see how this works, but
'strange' could be 'rum' (similar in meaning) and 'rum' is present in the answer.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for ruminate that I've seen before include "deliberate" , "Cogitate" , "Contemplate" , "'Reflect deeply, chew the cud (8)'" , "Ponder or meditate in mature way" .)