Moist like a shellfish? (6)
I believe the answer is:
clammy
'moist' is the definition.
(thesaurus)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for clammy that I've seen before include "Unpleasantly cool and humid" , "Dank" , "Unpleasantly damp and sticky" , "(Of weather) sticky" , "Moist and adhesive" .)