The bird did fly in to get under cover (6)
I believe the answer is:
hidden
'under cover' is the definition.
(thesaurus)
'the bird did fly in' is the wordplay.
'the bird' becomes 'hen' (hen is a kind of bird).
'fly' indicates anagramming the letters.
'in' indicates putting letters inside.
'did' with letters rearranged gives 'idd'.
'hen' placed around 'idd' is 'HIDDEN'.
'to get' acts as a link.
(Other definitions for hidden that I've seen before include "Latent" , "Consealed or secret" , "Unseen" , "Obscure" , "Abstruse" .)