Henry has just one objection to this on the menu (7)
I believe the answer is:
halibut
'menu' is the definition.
The definition and answer can be both things that one consumes for nourishment as well as being singular nouns.
Perhaps there's an association between them I don't understand?
'henry has just one objection to this on' is the wordplay.
'henry' becomes 'hal' (short for Henry).
'has' means one lot of letters go next to another.
'just one' becomes 'i' (Roman numeral. I am not sure about the 'just' bit.).
'objection' becomes 'but' (as in 'no ifs, no buts').
'to this on' means one lot of letters go next to another.
'hal'+'i'+'but'='HALIBUT'
'the' acts as a link.
Can you help me to learn more?
(Other definitions for halibut that I've seen before include "Utah lib (anag)" , "Large flatfish, tasty to eat" , "Marine food fish" , "Fishy sort" , "Large food fish" .)