Teacher is funny, little child being first one to grin (8,3)
I believe the answer is:
cheshire cat
'one to grin' is the definition.
(Lewis Carroll character famous for his smile)
'teacher is funny little child being first' is the wordplay.
'funny' indicates anagramming the letters.
'little child' becomes 'ch' (abbreviation for child. I am not sure about the 'little' bit.).
'being first' is a charade indicator (letters next to each other).
'teacher'+'is'='teacheris'
'teacheris' anagrammed gives 'eshirecat'.
'eshirecat' after 'ch' is 'CHESHIRE CAT'.
(Other definitions for cheshire cat that I've seen before include "Carroll's smiling feline" , "Its grin disappeared last" , "Grinning feline" , "I smile when all else is gone" , "Wonderland animal" .)