Fish with a lime chunk only (7)
I believe the answer is:
halibut
'fish' is the definition.
(I know that halibut is a type of fish)
'with a lime chunk only' is the wordplay.
'with' says to put letters next to each other.
'a lime chunk' becomes 'hali' (I can't explain this - if you can you should give a lot more credence to this answer).
'only' becomes 'but' (but can mean only - eg 'life is but a dream').
'hali' next to 'but' is 'HALIBUT'.
Can you help me to learn more?
(Other definitions for halibut that I've seen before include "Something fishy here" , "Fish found in Bali hut" , "Large flatfish used as food" , "Marine food fish" , "One's scaled" .)