Road covering very undulating (4)
I believe the answer is:
wavy
'undulating' is the definition.
(thesaurus)
'road covering very' is the wordplay.
'road' becomes 'way' (I've seen this in other clues).
'covering' means one lot of letters goes inside another.
'very' becomes 'v' (abbreviation).
'way' enclosing 'v' is 'WAVY'.
(Other definitions for wavy that I've seen before include "Curly (hair)" , "full of bends" , "Rippled" , "Sinuous" , "Undulating" .)