Learned man rested outside commercial vehicle (6)
I believe the answer is:
savant
'learned man' is the definition.
(I've seen this before)
'rested outside commercial vehicle' is the wordplay.
'rested' becomes 'sat' (to sit is to rest).
'outside' means one lot of letters goes inside another (some letters go outside others).
'commercial vehicle' becomes 'van' (I've seen this before).
'sat' placed around 'van' is 'SAVANT'.
(Other definitions for savant that I've seen before include "He displays erudition" , "Scholarly person" , "Learned man" , "A learned person in France (6)" , "Wise fellow" .)