Pet let out some livestock (6)
I believe the answer is:
cattle
'some livestock' is the definition.
(I've seen this before)
'pet let out' is the wordplay.
'pet' becomes 'cat' (cats are often kept as pets).
'out' indicates anagramming the letters (out can mean wrong or inaccurate).
'let' is an anagram of 'tle'.
'cat'+'tle'='CATTLE'
(Other definitions for cattle that I've seen before include "Jersey and Guernsey?" , "Domesticated bovine animals" , "Where it naturally lies (Latin)" , "Beasts of pasture" , "feature of 21/23 [NATIVITY SCENE]" .)