Graceful animal is so meek inside (7)
I believe the answer is:
lissome
'graceful' is the definition.
(I've seen this before)
'animal is so meek inside' is the wordplay.
'inside' indicates a hidden word.
'LISSOME' is hidden within 'animal is so meek'.
(Other definitions for lissome that I've seen before include "Moving supply" , "pliable" , "So smile, being agile and lithe" , "Oil mess (anag)" , "Thin - supple - graceful" .)