Oyster? Simple to swallow half of it (6)
I believe the answer is:
native
'oyster?' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'simple to swallow half of it' is the wordplay.
I cannot quite understand how this works, but
'it' could be 't' (abbreviation. e.g. in 'tis) and 't' is present in the answer.
'simple' could be 'naive' (similar in meaning) and 'naive' is found in the remaining letters.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for native that I've seen before include "Belonging to a particular place by birth" , "One who belongs to place by birth" , "One born in a certain place" , "mother" , "Endemic - aborigine" .)