Parts of Soho even show a certain polish! (5)
I believe the answer is:
sheen
'a certain polish' is the definition.
'sheen' can be an answer for 'polish' (I've seen this before). I'm unsure of the 'a certain' bit.
'parts of soho even' is the wordplay.
'parts of soho' becomes 'sh' (I can't explain this - if you can you should give a lot more credence to this answer).
'even' becomes 'een' (old-fashioned contraction).
'sh'+'een'='SHEEN'
'show' is the link.
Can you help me to learn more?
(Other definitions for sheen that I've seen before include "Patina" , "Oil slick" , "Polish" , "splendid clothing" , "Soft lustre on a surface" .)