They mean no, you’re not trying to get a hitch (6,4)
I believe the answer is:
thumbs down
'they mean no you're' is the definition.
I don't know anything about this answer so I cannot tell whether it can be defined by this definition.
'not trying to get a hitch' is the wordplay.
I cannot really see how this works, but
'not' could be 'o' (I've seen this in other clues) and 'o' is located in the answer.
'hitch' could be 'thumb' (hitch-hiking) and 'thumb' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for thumbs down that I've seen before include "Sign of rejection" , "damning verdict" .)