Seafood: have most of mine (6)
I believe the answer is:
scampi
'seafood' is the definition.
(type of seafood)
'have most of mine' is the wordplay.
'have' becomes 'scam' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'most of' means to remove the last letter.
'mine' becomes 'pit' (down the pit).
'pit' with its last letter taken away is 'pi'.
'scam'+'pi'='SCAMPI'
Can you help me to learn more?
(Other definitions for scampi that I've seen before include "Tasty prawns in batter" , "Dish of deep-friend prawns" , "Fish dish, often in rings" , "Dish of fried shrimp or prawns" , "Large prawns as food" .)