Old browser? A bot runs ours loosely (12)
I believe the answer is:
brontosaurus
'old browser?' is the definition.
(extinct animal which fed by browsing)
'a bot runs ours loosely' is the wordplay.
'loosely' indicates anagramming the letters.
'a'+'bot'+'runs'+'ours'='abotrunsours'
'abotrunsours' with letters rearranged gives 'BRONTOSAURUS'.
(Other definitions for brontosaurus that I've seen before include "Prehistoric thunderer?" , "Large herbivorous dinosaur" , "Prehistoric beast (thunder lizard)" , "Dinosaur with a long neck and tail" , "Huge herbivorous Jurassic reptile" .)