Young flier heading skyward without impediment (5)
I believe the answer is:
owlet
'young flier' is the definition.
(I've seen this before)
'heading skyward without impediment' is the wordplay.
'heading skyward' says the letters should be written backwards (in a down clue, heading 'up').
'without' becomes 'wo' (abbreviation of 'without', normally with a slash).
'impediment' becomes 'let' ('let' could historically mean a hindrance).
'wo' in reverse letter order is 'ow'.
'ow'+'let'='OWLET'
(Other definitions for owlet that I've seen before include "Young nocturnal bird of prey" , "Small bird of prey from Africa and Asia" , "Little hooter?" , "Little nocturnal bird" , "One may give a little screech" .)