It's said to produce a smile (6)
I believe the answer is:
cheese
'said to produce a smile' is the definition.
(say 'cheese'!)
'it's' is the wordplay.
I cannot quite understand how this works, but
'it's' could be 'es' ('e' can mean 'electronic' which is similar to 'IT') and 'es' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for cheese that I've seen before include "Food made from milk curds" , "See 22" , "Edam or cheddar, say" , "Wensleydale, Stilton etc" , "Milk product like gorgonzola" .)