Gene travelling round in motor (6)
I believe the answer is:
engine
'motor' is the definition.
(I know that motor can be written as engine)
'gene travelling round in' is the wordplay.
'travelling' is an anagram indicator.
'round' means one lot of letters goes inside another.
'gene' anagrammed gives 'enge'.
'enge' enclosing 'in' is 'ENGINE'.
(Other definitions for engine that I've seen before include "Machine supplying power" , "Machine converting energy into motion" , "Motive machine" , "Machine with moving parts" , "machinery" .)