Bird causing Hemingway perhaps to lose way (4)
I believe the answer is:
erne
'bird' is the definition.
(erne is a kind of bird)
'hemingway perhaps to lose way' is the wordplay.
'hemingway perhaps' becomes 'ernest' (Ernest Hemingway).
'to lose' indicates named letters should be taken away.
'way' becomes 'st'.
'ernest' with 'st' taken away is 'ERNE'.
'causing' is the link.
(Other definitions for erne that I've seen before include "White-tailed eagle" , "Large bird" , "River and lake of the North" , "flyer in the main" , "Irish river, loughs; sea bird" .)