Buyer's pro tem infractus est (6)

I believe the answer is:

emptor

'buyer's' is the definition.
(synonyms)

I don't understand the rest of the clue.

(Other definitions for emptor that I've seen before include "'Caveat..., let the buyer beware (6)'" , "A Latin buyer - let him caveat" , "... emptor, let the buyer beware" , "See 15" .)

I've seen this clue in The Guardian.

Want a hint initially instead of a full solution? Install my app