Ridiculously good parts in snail for instance (9)
I believe the answer is:
gastropod
'snail for instance' is the definition.
(snails are gastropods)
'ridiculously good parts' is the wordplay.
'ridiculously' indicates an anagram (I've seen this in other clues).
'good'+'parts'='goodparts'
'goodparts' is an anagram of 'GASTROPOD'.
'in' acts as a link.
(Other definitions for gastropod that I've seen before include "sluggish type" , "Little creature" , "Eg, a snail or slug" , "slug, perhaps" , "Escargot" .)