Reportedly go off bird (4)
I believe the answer is:
tern
'bird' is the definition.
(tern is a kind of bird)
'reportedly go off' is the wordplay.
'reportedly' shows a homophone (sound like).
'go off' becomes 'turn' (I've seen this before).
'turn' is a homophone of 'TERN'.
(Other definitions for tern that I've seen before include "Gull-like seabird" , "Three-masted schooner" , "Seagull" , "Seabird related to the gull" , "Long-winged aquatic bird" .)