Source of disease: cure a bit tricky, needing months (9)
I believe the answer is:
bacterium
'source of disease' is the definition.
Although both the answer and definition are singular nouns, I don't understand how they can define each other.
'cure a bit tricky needing months' is the wordplay.
'tricky' is an anagram indicator.
'needing' says to put letters next to each other.
'months' becomes 'm'.
'cure'+'a'+'bit'='cureabit'
'cureabit' is an anagram of 'bacteriu'.
'bacteriu'+'m'='BACTERIUM'
Can you help me to learn more?
(Other definitions for bacterium that I've seen before include "Fundamental" , "health risk?" , "Micro-organism that can cause disease" , "germ?" .)