Two ducks in Kerry built bird colony (7)
I believe the answer is:
rookery
'bird colony' is the definition.
(I've seen this before)
'two ducks in kerry built' is the wordplay.
'two ducks' becomes 'oo'.
'in' is an insertion indicator.
'built' is an anagram indicator.
'kerry' is an anagram of 'rkery'.
'oo' put inside 'rkery' is 'ROOKERY'.
(Other definitions for rookery that I've seen before include "Colony of penguins or seals" , "Breeding colony of birds, also of seals or turtles" , "Community of birds" , "Breeding-place of birds, penguins, seals" , "Nesting-place" .)