Soaring seabird swallows it whole (6)
I believe the answer is:
entire
'whole' is the definition.
(similar in meaning)
'soaring seabird swallows it' is the wordplay.
'soaring' says the letters should be written backwards (in a down clue, letters 'soar' up).
'seabird' becomes 'erne' (I've seen this before).
'swallows' indicates putting letters inside.
'erne' enclosing 'it' is 'eritne'.
'eritne' reversed gives 'ENTIRE'.
(Other definitions for entire that I've seen before include "in one piece" , "Whole; unbroken" , "Envelope" , "Lure" , "Complete, intact" .)