Bird: I'm not sure able in the end to soar? (3)
I believe the answer is:
emu
'bird' is the definition.
(emu is a kind of bird)
'i'm not sure able in the end to soar?' is the wordplay.
'i'm not sure' becomes 'um' (expression of hesitation).
'in the end' says to take the final letters.
'to soar?' says the letters should be written backwards (I've seen 'soaring' mean this (in a down clue, letters 'soar' up)).
The final letter of 'able' is 'e'.
'um'+'e'='ume'
'ume' reversed gives 'EMU'.
(Other definitions for emu that I've seen before include "Fast runner in Oz" , "Extinct bird" , "Native Australian bird" , "Aussie bird" , "Australian running bird." .)