Bird lands on island to find drink (7)
I believe the answer is:
martini
'drink' is the definition.
(martini is a kind of drink)
'bird lands on island' is the wordplay.
'bird' becomes 'martin' (martin is a kind of bird).
'lands on' means one lot of letters go next to another (in a down clue, some letters go on top of others).
'island' becomes 'i' (geographical abbreviation).
'martin'+'i'='MARTINI'
'to find' is the link.
(Other definitions for martini that I've seen before include "Sienese painter" , "obtained from a bottle" , "James Bond's drink of choice" , "In glass, one's dry" , "Alternative name for Simone Memmi, pre-Renaissance Italian painter" .)