Long gradient with no parking (4)
I believe the answer is:
itch
'long' is the definition.
(thesaurus)
'gradient with no parking' is the wordplay.
'gradient' becomes 'pitch'.
'with no' is a deletion indicator.
'parking' becomes 'p'.
'pitch' with 'p' taken away is 'ITCH'.
(Other definitions for itch that I've seen before include "great desire" , "Longing; anag. of 19" , "Slight irritation" , "Something that needs a scratch" , "Nagging wish" .)