Driving force
'driving force' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for motor that I've seen before include "go quickly" , "Internal combustion engine" , "(Transport using) engine" , "Car (colloq,)" , "Car; powered machine" .)
'driving force' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for steam that I've seen before include "Pre-digital" , "enthusiasm" , "12 dn water vapour" , "Vapourised water" , "Type of power" .)
'driving force' is the definition.
(impetus is a kind of driving force)
This is all the clue.
(Other definitions for impetus that I've seen before include "Momentum, stimulus" , "Driving force, forward movement" , "Imputes to force with which a body moves" , "Drive" , "Motivation" .)
'driving force' is the definition.
(synonyms)
This is all the clue.
(Other definitions for thrust that I've seen before include "Push forward as with fencing sword" , "Push suddenly forward" , "press" , "Force from jet engine" , "Force engine generates" .)