Tom perhaps is infected by suspect rash -- must get purging (9)
I believe the answer is:
catharsis
'purging' is the definition.
(I know that catharsis is a type of purging)
'tom perhaps is infected by suspect rash' is the wordplay.
I cannot really see how this works, but
'tom' could be 'cat' (a tom is a male cat) and 'cat' is found in the answer.
'is' is found in the answer.
an anagram of 'rash' is 'hars' which is present in the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
'must get' acts as a link.
Can you help me to learn more?
(Other definitions for catharsis that I've seen before include "purging process" , "cleansing'" , "Release of feelings" , "emotional event" , "Purification - is rash act (anag)" .)