Crossword Genius

Battery is run down in motorway (9)

Ross

I believe the answer is:

artillery

I'm a little stuck... Click here to teach me more about this clue!

'battery' is the definition.
(thesaurus)

'run down in motorway' is the wordplay.
I cannot quite understand how this works, but
'run' could be 'r' (cricket abbreviation) and 'r' is present in the answer.
'down' could be 'ill' (I've seen this in another clue) and 'ill' is found within the answer.
This explanation may well be incorrect...

'is' is the link.

Can you help me to learn more?

(Other definitions for artillery that I've seen before include "Heavy guns" , "Heavy weapons" , "Large guns for army in land war" , "Gunners" , "Guns, cannons etc" .)

I've seen this clue in The Telegraph.
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