Rear cattle? That's bad advice (3,5)
I believe the answer is:
bum steer
'bad advice' is the definition.
(I've seen this in another clue)
'rear cattle?' is the wordplay.
'rear' becomes 'bum' (synonyms).
'cattle?' becomes 'steer' (steer is a kind of cattle).
'bum'+'steer'='BUM STEER'
'that's' is the link.
(Other definitions for bum steer that I've seen before include "misleading information?" , "Dud" .)