Apes playing with large part of flower (5)
I believe the answer is:
sepal
'part of flower' is the definition.
(I know that sepal is part of calyx)
'apes playing with large' is the wordplay.
'playing' is an anagram indicator.
'with' says to put letters next to each other.
'large' becomes 'l' (eg in clothes sizes).
'apes' anagrammed gives 'sepa'.
'sepa'+'l'='SEPAL'
(Other definitions for sepal that I've seen before include "Part of a flower - peals (anag)" , "Enclosing part of flower" , "Part of a flower's outer envelope" , "Violet" , "Part of a flowering plant" .)