Those people taken in by Ernest Hemingway (4)
I believe the answer is:
them
'those people' is the definition.
('they' refers to a group of people)
'in by ernest hemingway' is the wordplay.
'in' indicates a hidden word.
'THEM' can be found hidden inside 'by ernest hemingway'.
'taken' is the link.
(Other definitions for them that I've seen before include "... in another case, they" , "Perhaps, the Opposition" , "(To/from) those people" , "Those people (as object)" , "Let -- eat cake" .)