Bird -- I check on unfamiliar sort (7)
I believe the answer is:
ostrich
'bird' is the definition.
(ostrich is a kind of bird)
'i check on unfamiliar sort' is the wordplay.
'check' becomes 'ch' (I've seen this in other clues**).
'on' is a charade indicator (letters next to each other).
'unfamiliar' indicates anagramming the letters.
'sort' anagrammed gives 'ostr'.
'i'+'ch'='ich'
'ich' after 'ostr' is 'OSTRICH'.
(Other definitions for ostrich that I've seen before include "Runner" , "The head-in-the-sand bird" , "A bird for the shirt co." , "with a big nest egg" , "To Chris (anag)" .)