Miss popular baked good (6)
I believe the answer is:
muffin
'baked good' is the definition.
(muffin is a kind of baked good)
'miss popular' is the wordplay.
'miss' becomes 'muff' (I've seen this before).
'popular' becomes 'in' ('in' can mean trendy).
'muff'+'in'='MUFFIN'
(Other definitions for muffin that I've seen before include "baked treat" , "Yeast cake eaten hot" , "Have IMF fun with the cake" , "Round raised cake, often split and toasted" , "Tea cake" .)