Cleansing of felines concealing messy hairs (9)
I believe the answer is:
catharsis
'cleansing' is the definition.
(catharsis is a kind of cleansing)
'felines concealing messy hairs' is the wordplay.
'felines' becomes 'cats' (cat is a kind of feline).
'concealing' means one lot of letters goes inside another.
'messy' indicates anagramming the letters.
'hairs' with letters rearranged gives 'harsi'.
'cats' enclosing 'harsi' is 'CATHARSIS'.
'of' acts as a link.
(Other definitions for catharsis that I've seen before include "Release of feelings" , "Emotional purge" , "relief of tensions" , "The release of pent-up emotions" , "Emotional release" .)