Unusually fine story that’s hard to describe (9)
I believe the answer is:
ineffable
'hard to describe' is the definition.
I can't tell whether this definition defines the answer.
'unusually fine story' is the wordplay.
'unusually' indicates an anagram.
'story' becomes 'fable' (fable is a kind of story).
'fine' anagrammed gives 'inef'.
'inef'+'fable'='INEFFABLE'
'that's' is the link.
Can you help me to learn more?
(Other definitions for ineffable that I've seen before include "Defying description" , "Unutterable, too great to be described" , "impossible to describe" , "Indescribable in words" , "Inexpressible" .)