Part of shoe, regularly knocked, shows freshness (9)
I believe the answer is:
insolence
'freshness' is the definition.
(I know that freshness can be written as insolence)
'part of shoe regularly knocked' is the wordplay.
'part of shoe' becomes 'insole' ('insole' is part of 'shoe').
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
The alternate letters of 'knocked' are 'nce'.
'insole'+'nce'='INSOLENCE'
'shows' acts as a link.
(Other definitions for insolence that I've seen before include "Rudeness, disrespect" , "Rudeness, impudence" , "Front" , "Hubris" , "Cheek, irreverence" .)