Possibly calls every second, say for instance (3)
I believe the answer is:
veg
'instance' is the definition.
Both the answer and definition are singular nouns.
Maybe there's a link between them I don't understand?
'possibly calls every second say' is the wordplay.
I cannot quite see how this works, but
'say' could be 'eg' (short for 'exempli gratia', 'for example' in Latin) and 'eg' is found in the answer.
'every second' could be 'v' (2nd letter of 'every') and 'v' is found in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
'for' is the link.
Can you help me to learn more?
(Other definitions for veg that I've seen before include "Eg, sprouts, parsnips" , "Potatoes and cabbages etc" , "Food plants" , ""Meat and two __ "" , "Slob?" .)