Rodent, second to appear in bazaar (6)
I believe the answer is:
marmot
'rodent' is the definition.
(marmot is a kind of rodent)
'second to appear in bazaar' is the wordplay.
'second' becomes 'mo' (both are short periods of time).
'to appear in' is an insertion indicator.
'bazaar' becomes 'mart' (both can mean a market).
'mo' going inside 'mart' is 'MARMOT'.
(Other definitions for marmot that I've seen before include "Furry burrowing rodent" , "wild rodent" , "Stout, burrowing rodent" , "Small burrowing animal of the squirrel family" , "Creature" .)