Large parrots (6)
I believe the answer is:
'large parrots' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for macaws that I've seen before include "Brightly-coloured parrots" , "Long-tailed, brilliantly-coloured parrots" , "More than one bird" , "Long-tailed parrots of Central and South America" , "Birds" .)