Mollusc graduate dissected by themselves (7)
I believe the answer is:
abalone
'mollusc' is the definition.
(abalone is a kind of mollusc)
'graduate dissected by themselves' is the wordplay.
I cannot quite see how this works, but
'graduate' could be 'ba' (someone with a Bachelor of Arts degree) and 'ba' is found in the answer.
'by themselves' could be 'alone' (I've seen this in another clue) and 'alone' is found within the answer.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for abalone that I've seen before include "One lives in a shell" , "Sea food must be found" , "Edible shellfish, sea-ear" , "Would you be able on a US shellfish?" , "Shell used for decoration" .)