What's odd about wet weather bringing disease? (7)
I believe the answer is:
murrain
'disease?' is the definition.
(murrain is a kind of health problem)
'what's odd about wet weather' is the wordplay.
'what's odd' becomes 'rum' (rum can mean strange or dubious).
'about' is a reversal indicator.
'wet weather' becomes 'rain' (rain is wet weather).
'rum' written backwards gives 'mur'.
'mur'+'rain'='MURRAIN'
'bringing' is the link.
(Other definitions for murrain that I've seen before include "Cattle-plague" , "Cattle disease" , "Cattle plague" .)