Flight concealed by the giraffes (6)
I believe the answer is:
hegira
'flight' is the definition.
(hegira is a kind of flight)
'concealed by the giraffes' is the wordplay.
'concealed' says the answer is hidden in the clue.
'HEGIRA' is hidden in the letters of 'by the giraffes'.
(Other definitions for hegira that I've seen before include "departure" , "Flight to safety" , "famous flight" , "The flight of Muhammad from Mecca in AD 622, from which Muslim era is measured" .)