One addict, I fancy, could show this (10)
I believe the answer is:
dedication
'show this' is the definition.
The definition suggests a singular noun which matches the answer.
'one addict i fancy' is the wordplay.
'fancy' indicates an anagram.
'one'+'addict'+'i'='oneaddicti'
'oneaddicti' is an anagram of 'DEDICATION'.
'could' is the link.
(Other definitions for dedication that I've seen before include "tribute" , "with which author often starts work" , "Commitment; inscription" , "Devotion (to a task)" .)