What’s to the south of the Himalayas? Not a poor state (13)
I believe the answer is:
indisposition
'a poor state' is the definition.
(state of being poorly or indisposed)
'what's to the south of the himalayas? not' is the wordplay.
I cannot really see how this works, but
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is found within the answer.
'south' could be 's' (abbreviation) and 's' is found in the answer.
'of' could be 'o' and 'o' is found within the answer.
'not' could be 'o' (I've seen this in other clues) and 'o' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
(Other definitions for indisposition that I've seen before include "Slight illness" , "Disinclination" , "State of being unwell or unfit" .)