Count a cuckoo as a tropical bird (6)
I believe the answer is:
toucan
'a tropical bird' is the definition.
(I've seen this before)
'count a cuckoo' is the wordplay.
'cuckoo' indicates an anagram.
'count'+'a'='counta'
'counta' anagrammed gives 'TOUCAN'.
'as' acts as a link.
(Other definitions for toucan that I've seen before include "Tropical bird with large bill" , "Bird with large colourful beak" , "arboreal dweller" , "Sounds as if a pair is able for the tropical bird" , "Tropical American bird with immense beak" .)