Top at an auction (6)
I believe the answer is:
outbid
'top at an auction' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for outbid that I've seen before include "Offer more for something than (another person)" , "Make a higher offer than another" , "Offer more then competitors at auction" , "Offer more than (another in auction)" , "as 14 might do to 3 or 26" .)