Influence remarkable old motoring indication (4,6)
I believe the answer is:
hand signal
'old motoring indication' is the definition.
The definition suggests a singular noun which matches the answer. I also know that 'indication' relates to this answer.
'influence remarkable' is the wordplay.
'influence' becomes 'hand' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'remarkable' becomes 'signal' (signal can mean striking or noteworthy).
'hand'+'signal'='HAND SIGNAL'
Can you help me to learn more?
(Another definition for hand signal that I've seen is " Manual indication by road user".)