Eatery some discovered in Eriskay (5)
I believe the answer is:
'eatery' is the definition.
(I've seen this in another clue)
'some discovered in eriskay' is the wordplay.
'some' indicates the answer is hidden within the clue (some of the parts of the word are used).
'DINER' can be found hidden inside 'discovered in eriskay'.
(Other definitions for diner that I've seen before include "(One using) restaurant car" , "Small American eatery" , "One taking a meal" , "US cafe" , "US eatery" .)