Flier powerless to loosen girdle? (6)
I believe the answer is:
glider
'flier' is the definition.
(I have seen 'quiet flier' mean 'glider' so perhaps 'flier' could also mean 'glider')
'loosen girdle?' is the wordplay.
'loosen' is an anagram indicator.
'girdle' anagrammed gives 'GLIDER'.
'powerless to' is the link.
This may not be right. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for glider that I've seen before include "Aircraft supported solely by air" , "Girdle for silent flier" , "Powerless aircraft" , "quiet flier" , "Unpowered plane" .)