Henry and I only have fish (7)
I believe the answer is:
halibut
'fish' is the definition.
(I know that halibut is a type of fish)
'henry and i only' is the wordplay.
'henry' becomes 'hal' (short for Henry).
'and' says to put letters next to each other.
'only' becomes 'but' (but can mean only - eg 'life is but a dream').
'hal'+'i'+'but'='HALIBUT'
'have' acts as a link.
(Other definitions for halibut that I've seen before include "Largest flatfish" , "Large flatfish used as food" , "Fishy sort" , "Fish found in Bali hut" , "One's scaled" .)