For starters, Ratty and Mole regularly seeing Mr Toad drive aggressively (6)
I believe the answer is:
ramrod
'drive aggressively' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Perhaps you can see an association between them that I can't see?
'for starters ratty and mole regularly seeing mr toad' is the wordplay.
'for starters' suggests taking the first letters.
'regularly seeing mr toad' becomes 'rod' (I can't justify this - if you can you should give a lot more credence to this answer).
The initial letters of 'ratty and mole' is 'ram'.
'ram'+'rod'='RAMROD'
Can you help me to learn more?
(Other definitions for ramrod that I've seen before include "Stern and inflexible person - part of a musket's equipment" , "Cannoneer's tool" , "It's used to push a charge into a firearm" , "Device for charging gun, proverbially stiff" , "Strict disciplinarian" .)