Bluish-grey fruit, large (5)
I believe the answer is:
pearl
'bluish-grey' is the definition.
I can't judge whether this defines the answer.
'fruit large' is the wordplay.
'fruit' becomes 'pear' (pear is a kind of fruit).
'large' becomes 'L' (eg in clothes sizes).
'pear'+'l'='PEARL'
Can you help me to learn more?
(Other definitions for pearl that I've seen before include "Gem; an attacked Harbor" , "Object of great worth" , "Precious jewel from the oyster" , "Oyster growth" , "something highly valued" .)