Donald's first drink in the valley (4)
I believe the answer is:
dale
'the valley' is the definition.
(dale is a kind of valley)
'donald's first drink' is the wordplay.
'donald's first' becomes 'd' (ast letter of 'donald').
'drink' becomes 'ale' (type of beer).
'd'+'ale'='DALE'
'in' acts as a link.
(Other definitions for dale that I've seen before include "Valley; Trollope's Bell and Lily" , "See 8" , "Lead into poetic valley" , "Open valley" , "Valley, as in Yorkshire" .)