I love to eat after one (6)
I believe the answer is:
iodine
'i' is the definition.
(I is the chemical symbol for iodine)
'love to eat after one' is the wordplay.
'love' becomes 'o' (love means zero in tennis).
'to eat' becomes 'dine' (to dine is to eat a meal).
'after' says to put letters next to each other.
'one' becomes 'i' (Roman numeral).
'o'+'dine'='odine'
'odine' put after 'i' is 'IODINE'.
(Other definitions for iodine that I've seen before include "Antiseptic found in seaweed" , "Element, atomic number 53" , "Solution applied to wounds as an antiseptic" , "Tincture for cuts" , "Element forming black crystals or violet vapour" .)