As we rather suspect, it's a bird (10)
I believe the answer is:
shearwater
'a bird' is the definition.
(shearwater is a kind of bird)
'as we rather suspect' is the wordplay.
'suspect' indicates an anagram.
'as'+'we'+'rather'='aswerather'
'aswerather' anagrammed gives 'SHEARWATER'.
'it's' acts as a link.
(Other definitions for shearwater that I've seen before include "Manx --, seabird" , "Bird" .)