Commanding officer painting racing vehicle (2-4)
I believe the answer is:
go-cart
'racing vehicle' is the definition.
(as in go-cart racing)
'commanding officer painting' is the wordplay.
'commanding officer' becomes 'GOC' (military abbreviation, general officer commanding).
'painting' becomes 'art' (painting is an art).
'goc'+'art'='GO-CART'
(Other definitions for go-cart that I've seen before include "Low racing vehicle" , "Got car (anag.)" , "Vehicle used for recreational racing - baby-walker" , "Child's vehicle" .)