Winger, surprisingly sleek, secures try almost (7)
I believe the answer is:
kestrel
'winger' is the definition.
(kestrel is a kind of bird)
'surprisingly sleek secures try almost' is the wordplay.
'surprisingly' is an anagram indicator (a surprising ordering of the letters).
'secures' means one lot of letters goes inside another.
'almost' means to remove the last letter (most of the word but not all of it).
'sleek' anagrammed gives 'kesel'.
'try' with its final letter taken away is 'tr'.
'kesel' placed around 'tr' is 'KESTREL'.
(Other definitions for kestrel that I've seen before include "Small type of falcon" , "Falcon that hovers" , "Falco tinnuculus" , "It takes mice" , "Small species of falcon" .)