Muse playing for the birds (4)
I believe the answer is:
emus
'birds' is the definition.
(emu is a kind of bird)
'muse playing' is the wordplay.
'playing' indicates an anagram.
'muse' with letters rearranged gives 'EMUS'.
'for the' is the link.
(Other definitions for emus that I've seen before include "Muse about flightless Australian birds" , "Aussie birds" , "Large flightless birds of Australia" , "Running birds" , "Fast, but not high-fliers" .)