Ten-foot sea midget (6)
I believe the answer is:
shrimp
'midget' is the definition.
(thesaurus)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for shrimp that I've seen before include "Seafood" , "Diminutive person" , "Small, weak person" , "School member" , "who gets bullied?" .)