An article to smile about, just a little (5)
I believe the answer is:
grain
'a little' is the definition.
(thesaurus)
'an article to smile about' is the wordplay.
'an article' becomes 'a' (the indefinite article in English).
'to smile' becomes 'grin' (grinning is a kind of smiling).
'about' means one lot of letters goes inside another.
'a' placed inside 'grin' is 'GRAIN'.
'just' is the link.
(Other definitions for grain that I've seen before include "Cereal crops" , "cereal crop" , "Enter into combat with" , "Particle of e.g. sand" , "bit of corn" .)