Very oddly observed, loves motorway and noise of cars (5)
I believe the answer is:
vroom
'and noise of cars' is the definition.
I can't tell whether this definition defines the answer.
'very oddly observed loves motorway' is the wordplay.
'oddly' means one should take alternating letters (letters in the odd-numbered positions are used).
'observed loves' becomes 'oo' (love means 0 in tennis. I am not sure about the 'observed' bit.).
'motorway' becomes 'M' (as in motorway names - Mo, M4 etc).
The alternating letters of 'very' are 'vr'.
'vr'+'oo'+'m'='VROOM'
Can you help me to learn more?
(Other definitions for vroom that I've seen before include "loud engine noise" , "(Of engine) make roaring sound (colloq.)" , "Fast revving sound" , "Fast-moving car noise" , "vehicle's noise" .)