Extremely large bird, a kind with no tail (7)
I believe the answer is:
titanic
'extremely large' is the definition.
(I've seen this before)
'bird a kind with no tail' is the wordplay.
'bird' becomes 'tit' (I've seen this before).
'kind' becomes 'nice' (I've seen this before).
'with no tail' means to remove the last letter.
'nice' with its last letter removed is 'nic'.
'tit'+'a'+'nic'='TITANIC'
(Other definitions for titanic that I've seen before include "Huge, epic" , "Gigantic like doomed ocean liner" , "Great ocean liner sunk by iceberg" , "Giant" , "Sinker" .)