Only half seasoned, bear with difficulty a gastropod (3,4)
I believe the answer is:
sea slug
'gastropod' is the definition.
(I know that sea slug is a type of gastropod)
'only half seasoned bear' is the wordplay.
'only half' means to take half the letters.
'bear' becomes 'lug' (both can mean to carry around).
'seasoned' cut in half is 'seas'.
'seas'+'lug'='SEA-SLUG'
'with difficulty a' is the link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for sea slug that I've seen before include "Shell-less marine mollusc" , "Creature" , "gastropod mollusc" .)