A choosy eater, teenage visitor returned sandwiches (5)
I believe the answer is:
vegan
'a choosy eater' is the definition.
'vegan' can be an answer for 'eater' (vegan is a kind of eater). I'm unsure of the 'a choosy' bit.
'teenage visitor returned sandwiches' is the wordplay.
'sandwiches' says the answer is hidden in the clue (the answer is sandwiched in by the clue).
'returned' shows that the letters should be reversed in order.
'nagev' can be found hidden inside 'teenage visitor'.
'nagev' back-to-front is 'VEGAN'.
Can you help me to learn more?
(Other definitions for vegan that I've seen before include "One not eating or using animal products" , "Avoider of animal products" , "One shunning animal products" , "Non-consumer of animal products" , "Strict abstainer from animal products" .)