Notice missing walls after former spouse became strange (6)
I believe the answer is:
exotic
'strange' is the definition.
(synonyms)
'notice missing walls after former spouse' is the wordplay.
I cannot really see how this works, but
'former' could be 'ex' (prefix meaning former or onetime) and 'ex' is located in the answer.
The remaining letters 'otic' 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).
'became' is the link.
Can you help me to learn more?
(Other definitions for exotic that I've seen before include "Originating in a foreign country" , "Foreign-looking" , "From far abroad" , "Alien; outlandish" , "Weird; strange" .)