Impatiently desiring drink getting euro at outset for pounds (5)
I believe the answer is:
eager
'impatiently desiring' is the definition.
'eager' can be an answer for 'desiring' (thesaurus). I'm not certain of the 'impatiently' bit.
I can't explain the rest of the clue.
(Other definitions for eager that I've seen before include "really keen" , "Fervent" , "It's a bore" , "Thirsty" , "Anxious" .)