Some inconspicuous car certainly is harder to find (7)
I believe the answer is:
scarcer
'harder to find' is the definition.
(something scarce is hard to find)
'some inconspicuous car certainly' is the wordplay.
'some' indicates a hidden word (some of the parts of the word are used).
'SCARCER' is hidden in the letters of 'inconspicuous car certainly'.
'is' acts as a link.
(Other definitions for scarcer that I've seen before include "More rare" , "Less common" , "More unusual" .)