Strange story about European mollusc (6)
I believe the answer is:
oyster
'mollusc' is the definition.
(oyster is a kind of mollusc)
'strange story about european' is the wordplay.
'strange' indicates an anagram.
'about' means one lot of letters goes inside another.
'european' becomes 'e' (abbreviation e.g. EU).
'story' anagrammed gives 'oystr'.
'oystr' going around 'e' is 'OYSTER'.
(Other definitions for oyster that I've seen before include "rather grey" , "Pearl-yielding shellfish" , "It produces pearls" , "Shade of greyish white" , "Type of mollusc" .)