When one has nothing to eat, this can come in a bottle! (6)
I believe the answer is:
iodine
'this can come in a bottle' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'when one has nothing to eat' is the wordplay.
'when one' becomes 'i' (Roman numeral. I am not sure about the 'when' bit.).
'has' means one lot of letters go next to another.
'nothing' becomes 'O' (O resembles 0).
'to eat' becomes 'dine' (to dine is to eat a meal).
'i'+'o'+'dine'='IODINE'
Can you help me to learn more?
(Other definitions for iodine that I've seen before include "Antiseptic found in seaweed" , "Solution applied to wounds as an antiseptic" , "Element used in medicine, photography and dyes" , "Infamous tablets in case of a nuclear emergency" , "Hanging tuft" .)