Forceful Republican enters in fall (7)
I believe the answer is:
driving
'forceful' is the definition.
(thesaurus)
'republican enters in fall' is the wordplay.
I cannot quite see how this works, but
'republican' could be 'r' (abbreviation) and 'r' is found in the answer.
'in' is found in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for driving that I've seen before include "Urging along" , "activity on the golf course" , "Pressing forward - in a car" , "In charge of a motor vehicle" , "Controlling; motoring" .)