Car valuation regularly neglected (4)
I believe the answer is:
auto
'car' is the definition.
(automobile)
'valuation regularly neglected' is the wordplay.
'regularly neglected' means one should take alternating letters (letters removed at regular intervals).
The alternating letters of 'valuation' are 'AUTO'.
(Other definitions for auto that I've seen before include "American vehicle" , "Motor vehicle, in short" , "Lincoln?" , "Prefix meaning self or same" , "Motor car (mainly US)" .)